How to restart a loop after capturing a wrong input?

How to restart a loop after capturing a wrong input?
because if i inputted a string or a character, my program captures the error but
the problem is that my program does not return from the initial spot or initial position
how can i solve that?this is my program

Code:

//This program can evaluate a 10th order polynomial single variable,
//can solve for statistical algorithms mainly mean, standard deviation
//and summation of data with a maximum of 10 data,
//can solve for ideal gas equation with the gas sample of nitrogen and
//can build a database of strings which can store of 16 strings with 128
//maximum characters, remove a string from the database, view the strings
//and search the strings inside the database

#include <stdio.h>
#include <conio.h>
#include <math.h>
#include <stdlib.h>
#include <string.h>

//Jerome H. Macatangay 10821333 MEE 2nd Year
//Andre Lloyd A. Torres 10832513 MEE 2nd Year

//Start Program
main(){
       int selection;
       //Variables for Polynomial Evaluation
       double polysum=0, x;
       int n, QA, m;
       //Variables for Statistical Algorithms
       int SA,a,b,sum=0,data[10];
       float mean;
       double calc,sd;
       //Variables for Ideal Gas Equations
       int unknown1;
       float P, V, R, M, T;
       R=8.3143/28.01;
       //Variables for String Database
       char string[16][128],temp[128],search[128];
       int i=0,s=0,y,rep,sel,eq;
       //Menu Selection Screen    
       do{
              selection=0;
              system("cls");
              printf("Menu Selection Screen\n\n");
              printf("1 - Polynomial Evaluation\n");
              printf("2 - Statistical Algorithms\n");
              printf("3 - Ideal Gas Law\n");
              printf("4 - String Database\n");
              printf("5 - Exit\n");
         
              scanf("%d",&selection);
              switch(selection){
                                case 1:
                                       do{
                                          do{
                                             system("cls");
                                             printf("Polynomial Evaluation\n\n");
                                             printf("Enter the Order of Polynomial (max. 10): ");
                                             scanf("%d",&n);
                                             if(n>10||n<1){
                                                           system("cls");
                                                           printf("Invalid input. Please try again!!!\n");
                                                           printf("Please press the spacebar to continue!!");
                                                           getche();
                                                           }
                                             }while(n>10||n<1);
                                             
                                             double poly[n+1];
                                             
                                             for(m=n;m>=0;m--){
                                                         printf("Please enter the constant for X raised to the %dth: ", m);
                                                         scanf("%lf",&poly[m]);
                                             }
                                             printf("Enter the value of X: ");
                                             scanf("%lf",&x);   
                                             for(m=n;m>=0;m--)
                                                               polysum+=poly[m]*pow(x,m);
                                             printf("The evaluated value of the %dth Order Polynomial  %.2lf\n", n, polysum);
                                             printf("Please press the spacebar to continue!!\n");
                                             getche();
                                             do{
                                                system("cls");
                                                printf("Do you want to repeat the computation?\n\n");
                                                printf("1 - Yes\n");
                                                printf("2 - No\n");
                                                scanf("%d", &QA);
                                                switch(QA){
                                                           case 1:
                                                                break;
                                                           case 2:
                                                                main();
                                                                break;
                                                           default:
                                                                   system("cls");
                                                                   printf("Invalid input. Please try again!!!\n");
                                                                   printf("Please press the spacebar to continue!!");
                                                                   getche();
                                                                   break;   
                                                           }
                                                }while(QA>2||QA<1);
                                                polysum=0;
                                             }while(QA==1);
                                     break;
                                case 2:
                                     do{
                                          sum=0;
                                          mean=0;
                                          calc=0;
                                          sd=0;
                                          system("cls");
                                          printf("Statistical Algorithms\n\n");
                                          printf("1 - Mean\n");
                                          printf("2 - Standard Deviation\n");
                                          printf("3 - Summation of data\n");
                                          printf("4 - Go Back to Menu Selection Screen\n");
                                                                   
                                          scanf("%d", &SA);
                                          switch(SA){
                                                     case 1:
                                                          do{
                                                             system("cls");
                                                             printf("Mean\n\n");
                                                             printf("Enter the Number of Data (max. 10): ");
                                                             scanf("%d", &b);
                                                             if(b>10||b<1){
                                                                           system("cls");
                                                                           printf("Invalid input. Please try again!!!\n");
                                                                           printf("Please press the spacebar to continue!!");
                                                                           getche();
                                                                           }
                                                             }while(b>10||b<1);
                                                          for(a=0;a<b;a++){
                                                             printf("Enter the Actual Values of Data %d: ", a+1);
                                                             scanf("%d",&data[a]);
                                                             }
                                                          for(a=0;a<b;a++){
                                                             sum=sum+data[a];
                                                             }
                                                          mean=(float)sum/a;
                                                          printf("The Mean of the Data is %f\n",mean);
                                                          printf("Please press the spacebar to continue!!");
                                                          getche();
                                                          break;
                                                     case 2:
                                                          do{
                                                             system("cls");
                                                             printf("Standard Deviation\n\n");
                                                             printf("Enter the Number of Data (max. 10): ");
                                                             scanf("%d", &b);
                                                             if(b>10||b==0){
                                                                           system("cls");
                                                                           printf("Invalid input. Please try again!!!\n");
                                                                           printf("Please press the spacebar to continue!!\n");
                                                                           getche();
                                                                           }
                                                             }while(b>10||b==0);
                                                          for(a=0;a<b;a++){
                                                             printf("Enter the Actual Values of Data %d: ", a+1);
                                                             scanf("%d",&data[a]);
                                                             }
                                                          if(b==1){
                                                             printf("The Standard Deviation the Data is 0\n");
                                                             printf("Please press the spacebar to continue!!");
                                                             getche();
                                                             break;
                                                                  }
                                                          for(a=0;a<b;a++){
                                                             sum=sum+data[a];
                                                             }
                                                          mean=(float)sum/a;
                                                          for(a=0;a<b;a++){
                                                             calc+=pow((data[a]-mean),2);
                                                             }
                                                          sd=sqrt(calc/(b-1));
                                                          printf("The Standard Deviation the Data is %lf\n",sd);
                                                          printf("Please press the spacebar to continue!!");
                                                          getche();
                                                          break;
                                                     case 3:
                                                          do{
                                                             system("cls");
                                                             printf("Summation of Data\n\n");
                                                             printf("Enter the Number of Data (max. 10): ");
                                                             scanf("%d", &b);
                                                             if(b>10||b<1){
                                                                           system("cls");
                                                                           printf("Invalid input. Please try again!!!\n");
                                                                           printf("Please press the spacebar to continue!!");
                                                                           getche();
                                                                           }
                                                             }while(b>10||b<1);
                                                          for(a=0;a<b;a++){
                                                             printf("Enter the Actual Values of Data %d: ", a+1);
                                                             scanf("%d",&data[a]);
                                                          }
                                                          for(a=0;a<b;a++){
                                                             sum=sum+data[a];
                                                             }
                                                          mean=(float)sum/a;
                                                          printf("The Summation of the Data is %d\n",sum);
                                                          printf("Please press the spacebar to continue!!");
                                                          getche();
                                                          break;
                                                     case 4:
                                                          main();
                                                          break;
                                                     default:
                                                             system("cls");
                                                             printf("Invalid Input. Please try again!!!\n");
                                                             printf("Please press the spacebar to continue!!");
                                                             getche();
                                                             break;
                                                     }
                                          }while(SA!=4);              
                                     break;
                                case 3:
                                     do{
                                           P=0;
                                           V=0;
                                           M=0;
                                           T=0;
                                system("cls");
                                printf("Ideal Gas Law\n");
                                printf("PV = mRT\n\n");
                                printf("Select one of the Unknowns\n");
                                printf("1 - P\n");
                                printf("2 - V\n");
                                printf("3 - M\n");
                                printf("4 - T\n");
                                printf("5 - Go Back to Menu Selection Screen\n");
                          
                                scanf("%d", &unknown1);                                 
                                switch(unknown1){
                                                 
                                                case 1:
                                                     do{
                                                     system("cls");
                                                     printf("Solving for Pressure\n\n");
                                                     printf("Volume (m^3): ");
                                                     scanf("%f",&V);
                                                     printf("Mass (kg): ");
                                                     scanf("%f",&M);
                                                     printf("Temperature (K): ");
                                                     scanf("%f",&T);
                                                     
                                                     if(V<=0){
                                                              system("cls");
                                                              printf("Invalid input of Volume\n");
                                                              printf("Please press the spacebar to continue!!");
                                                              getche();
                                                              }
                                                     if(M<=0){
                                                              system("cls");
                                                              printf("Invalid input of Mass\n");
                                                              printf("Please press the spacebar to continue!!");
                                                              getche();
                                                              }
                                                     if(T<=-273){
                                                              system("cls");
                                                              printf("Invalid input of Temperature\n");
                                                              printf("Please press the spacebar to continue!!");
                                                              getche();
                                                              }
                                                                                                                   
                                                     }while(V<=0||T<=-273||M<=0);
                                                     P = M*R*T/V;
                                                     printf("The Pressure is %f kPa\n",P);
                                                     printf("Please press the spacebar to continue!!");
                                                     getche();
                                                     
                                                     break;
                                                case 2:
                                                     do{
                                                     system("cls");
                                                     printf("Solving for Volume\n\n");
                                                     printf("Pressure (KPa): ");
                                                     scanf("%f",&P);
                                                     printf("Mass (kg): ");
                                                     scanf("%f",&M);
                                                     printf("Temperature (K): ");
                                                     scanf("%f",&T);
                                                                                                        
                                                     if(P<=0){
                                                              system("cls");
                                                              printf("Invalid input of Pressure\n");
                                                              printf("Please press the spacebar to continue!!");
                                                              getche();
                                                              }
                                                     if(M<=0){
                                                              system("cls");
                                                              printf("Invalid input of Mass\n");
                                                              printf("Please press the spacebar to continue!!");
                                                              getche();
                                                              }
                                                     if(T<=-273){
                                                              system("cls");
                                                              printf("Invalid input of Temperature\n");
                                                              printf("Please press the spacebar to continue!!");
                                                              getche();
                                                              }
                                                                                                                   
                                                     }while(P<=0||T<=-273||M<=0);
                                                     
                                                     V = M*R*T/P;
                                                     printf("The Volume is %f m^3\n",V);
                                                     printf("Please press the spacebar to continue!!");
                                                     getche();
                                                     break;
                                                case 3:
                                                     do{
                                                     system("cls");
                                                     printf("Solving for Mass\n\n");
                                                     printf("Pressure (KPa): ");
                                                     scanf("%f",&P);
                                                     printf("Volume (m^3): ");
                                                     scanf("%f",&V);
                                                     printf("Temperature (K): ");
                                                     scanf("%f",&T);

                                                     if(P<=0){
                                                              system("cls");
                                                              printf("Invalid input of Pressure\n");
                                                              printf("Please press the spacebar to continue!!");
                                                              getche();
                                                              }
                                                     if(V<=0){
                                                              system("cls");
                                                              printf("Invalid input of Volume\n");
                                                              printf("Please press the spacebar to continue!!");
                                                              getche();
                                                              }
                                                     if(T<=-273){
                                                              system("cls");
                                                              printf("Invalid input of Temperature\n");
                                                              printf("Please press the spacebar to continue!!");
                                                              getche();
                                                              }
                                                     
                                                     }while(P<=0||T<=-273||V<=0);
                                                     
                                                     M=(P*V)/(R*T);
                                                     printf("The Mass is %f kg\n",M);
                                                     printf("Please press the spacebar to continue!!");
                                                     getche();
                                                     break;
                                                case 4:
                                                     do{
                                                     system("cls");
                                                     printf("Solving for Temperature\n\n");
                                                     printf("Pressure (KPa): ");
                                                     scanf("%f",&P);
                                                     printf("Volume (m^3): ");
                                                     scanf("%f",&V);
                                                     printf("Mass (kg): ");
                                                     scanf("%f",&M);
                                                     
                                                     if(P<=0){
                                                              system("cls");
                                                              printf("Invalid input of Pressure\n");
                                                              printf("Please press the spacebar to continue!!");
                                                              getche();
                                                              }
                                                     if(V<=0){
                                                              system("cls");
                                                              printf("Invalid input of Volume\n");
                                                              printf("Please press the spacebar to continue!!");
                                                              getche();
                                                              }               
                                                     if(M<=0){
                                                              system("cls");
                                                              printf("Invalid input of Mass\n");
                                                              printf("Please press the spacebar to continue!!");
                                                              getche();
                                                              }
                                                     }while(P<=0||M<=0||V<=0);
                                                     
                                                     T = (P*V)/(M*R);
                                                     printf("The Temperature is %f K\n",T);
                                                     printf("Please press the spacebar to continue!!");
                                                     getche();
                                                     break;
                                                case 5:
                                                     main();
                                                     break;
                                                default:
                                                        system("cls");
                                                        printf("Invalid input, please try again!!\n");
                                                        printf("Please press the spacebar to continue!!");
                                                        getche();
                                                        break;     
                                                }
                                }while(unknown1 != 5);
                                break;
                                case 4:
                                   do{
                                      do{//Menu Selection Screen 
                                      do{ 
                                         system("cls");
                                         printf("String Database\n\n");
                                         printf("1 - Store a String to the Database\n");
                                         printf("2 - Remove a String from the Database\n");
                                         printf("3 - View Strings in the Database\n");
                                         printf("4 - Search a String in the Database\n");
                                         printf("5 - Go Back to Menu Selection Screen\n");
                                         scanf("%d",&selection);
                                         if(selection<1||selection>5){
                                         system("cls");
                                         printf("Invalid input. Please try again!!!\n");
                                         printf("Please press the spacebar to continue!!");
                                         getche();
                                         break;
                                         }
                                         }while(selection<1||selection>5);
                                         }while(selection!=1&&selection!=2&&selection!=3&&selection!=4&&selection!=5);
                                      
                                      if(selection==1){
                                                 do{//Store a String to the Database
                                                    system("cls");
                                                    printf("How many string do you want enter: ");
                                                    scanf("%d",&s);
                                                    for(i=-1;i<s;i++){
                                                    printf("Input a string: ");
                                                    gets(string[i]);
                                                    }
                                                    do{
                                                    do{
                                                       system("cls");
                                                       printf("String successfully added\n");
                                                       printf("Enter another string?\n\n");
                                                       printf("1 - Yes\n");
                                                       printf("2 - No\n");
                                                       scanf("%d",&rep);
                                                       if(rep<1||rep>2){
                                                       system("cls");
                                                       printf("Invalid input. Please try again!!!\n");
                                                       printf("Please press the spacebar to continue!!");
                                                       getche();
                                                       break;   
                                                       }
                                                       }while(rep<1||rep>2);
                                                       }while(rep!=1&&rep!=2);
                                                    }while(rep==1);
                                                 }
                                      else if(selection==2){
                                           do{//Remove a String from the Database
                                              system("cls");
                                              printf("Select position of string to remove:\n");
                                              for(i=0;i<s;i++)
                                                 printf("%d-%s\n",i+1,string[i]);
                                                 scanf("%d",&y);
                                                 strcpy(string[y-1],"");
                                                 s--;
                                                 strcpy(temp,string[s]);
                                              for(i=y;i<s;i++)
                                                 strcpy(string[i-1],string[i]);
                                                 strcpy(string[s-1],temp);
                                              do{
                                              do{
                                                 system("cls");
                                                 printf("String successfully deleted\n");
                                                 printf("Remove another string?\n\n");
                                                 printf("1 - Yes\n");
                                                 printf("2 - No\n");
                                                 scanf("%d",&rep);
                                                 if(rep<1||rep>2){
                                                 system("cls");
                                                 printf("Invalid input. Please try again!!!\n");
                                                 printf("Please press the spacebar to continue!!");
                                                 getche();
                                                 break;   
                                                 }
                                                 }while(rep<1||rep>2);
                                                 }while(rep!=1&&rep!=2);
                                              }while(rep==1);
                                           }
                                      else if(selection==3){//View Strings in the Database
                                           system("cls");
                                           for(i=0;i<s;i++)
                                              printf("%d - %s\n",i+1,string[i]);
                                              printf("Please press the spacebar to continue!!\n");
                                           getch();
                                           }
                                      else if(selection==4){
                                           do{//Search a String in the Database
                                              system("cls");
                                              eq=1;
                                              strcpy(search,"");
                                              for(i=-1;i<1;i++){
                                              printf("Enter string to search: ");
                                              gets(search);
                                              }
                                              for(i=0;i<s;i++){
                                                 eq=strcmp(string[i],search);
                                                 if(eq==0)
                                                 break;
                                                 }
                                              do{
                                                 system("cls");
                                                 if(eq==0){
                                                 printf("String matched\n");
                                                 printf("Position of searched string in array is %d\n",i+1);
                                                 printf("Please press the spacebar to continue!!\n");
                                                 getche();
                                                 }
                                                 else{
                                                 do{
                                                 printf("String not found\n");
                                                 printf("Search another string?\n\n");
                                                 printf("1 - Yes\n");
                                                 printf("2 - No\n");
                                                 scanf("%d",&rep);
                                                 if(rep<1||rep>2){
                                                 system("cls");
                                                 printf("Invalid input. Please try again!!!\n");
                                                 printf("Please press the spacebar to continue!!");
                                                 getche();
                                                 break;   
                                                 }
                                                 }while(rep<1||rep>2);
                                                 }
                                                 }while(rep!=1&&rep!=2);
                                              }while(rep==1);
                                           }
                                      else if(sel==5){
                                           main();
                                           break;
                                      }
                                      }while(sel!=5);
                                     break;
                                case 5:
                                     return 0;
                                     break;
                                default:
                                        system("cls");
                                        printf("Invalid input. Please try again!!!\n");
                                        printf("Please press the spacebar to continue!!");
                                        getche();
                                        break;
                                }
         }while(selection>5 || selection<=0);
}
       

 

if i understand correctly what you want

try this

Code:

................
char n1[10];
....................
do{
                                             system("cls");
                                             printf("Polynomial Evaluation\n\n");
                                             printf("Enter the Order of Polynomial (max. 10): ");
                                             [COLOR=Red]scanf("%s",&n1);
                                             n=atoi(n1);[/COLOR]
                                             if(n>10||n<1){
                                                           system("cls");
                                                           printf("Invalid input. Please try again!!!\n");
                                                           printf("Please press the spacebar to continue!!");
                                                           getche();
                                                           }
                                             }while(n>10||n<1);
............................

 

Thanks a lot for that!!!