c - loop not working properly, also needing data validation -

this may simple answer. have been programming c month. creating c-program user presented menu 1-4. menu options 1-3 ask user integer, when integer input, program writes or "draws" amount of "dots" or periods. each of first options same function, while loop, do-while loop, , loop respectively. way terminate program select 4 @ main menu.

my question how program loop , continue work properly. when execute program works correctly first time, when program loops main menu. no further options work. ie: if try input integer again "dot drawing" doesnt work correctly.

i having trouble validating input on either menu letters or "non numbers", @ moment if input letter breaks program.

im not sure , go this. im not needing code re-written, perhaps ideas of take it. i'll accept references or links provided. copy of incomplete program included below:

#include <stdio.h> #include <stdlib.h> #include <math.h>   int main() {     system("cls");  int programrun=0; int menuselection=0; int absmenuselection=0; int dotnumber=0; int countnumber=0; char enter;  while(programrun==0) { system("cls"); printf("\nplease make number selection\n"); printf("please select choice:\n"); printf("[1] while loop...\n"); printf("[2] do-while loop...\n"); printf("[3] loop...\n"); printf("[4] exit program...\n\n");  scanf("%d%c",&menuselection,&enter);     absmenuselection= abs(menuselection);      if (absmenuselection <1 || absmenuselection>4)     {     }     switch (absmenuselection)     {         case 1:             printf("\nplease input number amount of dots wish see...");             scanf("%d", &dotnumber);             if(dotnumber > 0)             {                 while(countnumber<dotnumber)                 {                 countnumber++;                 printf(".");                 }             }             else{                 printf("\nsorry, invalid response. have try again.\n");                 }             printf("\n");            system("pause");           break;          case 2:               printf("\nplease input number amount of dots wish see...");               scanf("%d", &dotnumber);               if(dotnumber > 0)               {                                 {                 countnumber++;                 printf(".",countnumber);                 }                 while( countnumber<dotnumber );               }               else               {                 printf("\nsorry, invalid response. have try again.\n");               }           printf("\n");           system("pause");           break;          case 3:               printf("\nplease input number amount of dots wish see...");               scanf("%d", &dotnumber);               if(dotnumber > 0)               {                   for(countnumber=0;countnumber<dotnumber;countnumber++)                   {                       printf(".",countnumber + 1);                   }               }               else               {                 printf("\nsorry, invalid response. have try   again.\n");               }            printf("\n");           system("pause");           break;          case 4:             while(programrun>1)             programrun=1;             printf("\nokay have nice day");             return 0;          default:                printf("\nsorry invalid statement, try again\n\n");                system("pause");     }}  system ("pause") ; return 0; } 

its working .....

set after each case: countnumber=0;

or try

if(dotnumber > 0)             { countnumber=0; /*rest */ } 

otherwise case 1: case 2: not work if try 2 times after giving dotnumber higher value @ first , lower @ last

edit: c library function void isdigit(int c) checks if passed character decimal digit character.

 if( isdigit(variablehere) )    {       //is digit    } 

sample o/p

please make number selection please select choice: [1] while loop... [2] do-while loop... [3] loop... [4] exit program...  1  please input number amount of dots wish see 4 .... press key continue . . .