Thread: Program Loops Forver! HELP!

hi guys need some help, my program seems to loop forever when any non-integer value is entered in an integer input

heres my code

Code:

/********************************
*                               *
*	Grade Calculator	*
*                               *
*********************************
*                               *
*      	James Daniel Archer	*
*                               *
*	15th December 2004      *
*                               *
*********************************
*                               *
*Input number of students, input*
*each students mark, calculate  *
*each students grade, output    *
*number of students, the average*
*grade for all students, & the  *
*number of students achieving   *
*each grade.                    *
*                               *
*********************************
*                               *
*Running the program:-          *
*   -Double click on the EXE    *
*    file to run the program.   *
*                               *
*********************************
*                               *
*References:-                   *
*   -N/A                        *
*                               *
*********************************
*                               *
*Restrictions:-                 *
*   -The program will not output*
*    a list of all students and *
*    their achieving grade.     *
*                               *
*********************************
*				*
*Error handling:-		*
*   -The program will ask the   *
*    user to re-input data if an*
*    error is detected. The     *
*    system will continue to ask*
*    the user to re-input the   *
*    data until an acceptable   *
*    value is entered.          *
*				*
*********************************
*				*
*See structure chart for more   *
*information.                   *
*				*
********************************/


/* Header Files */

#include <stdio.h>
#include <dos.h>

/* Functions */

void initialise(void);
void input(void);
void process(void);
void output(void);

/* Functions NOT Included On Stucture Chart
   These Functions Are Used For Program Presentation */

void intro(void);
void clear(void);
void load(void);

/* Global Variables */

int students, mark, count, failcount, passcount, meritcount, distinctioncount, total;
float average;
char fname[16], sname[16];

main()
{	/* Program Start */
   system("cls");	/* Clear Screen To Remove Data On Screen From Previous Programs */
   initialise();	/* Function Calls */
   intro();
   input();
   load();
   clear();
   process();
   load();
   clear();
   output();
   clear();
}	/* Program End */

void initialise(void)
{	/* Initialise Function Start */
   students=0;		/* Global Numeric Variables Initialised To 0 */
   mark=0;
   count=0;
   failcount=0;
   passcount=0;
   meritcount=0;
   distinctioncount=0;
   average=0;
}	/* Initialise Function End */

void input(void)
{	/* Input Function Start */
   printf("Please Input The Number of Students You Wish To Grade");
   printf(" \n");
   printf(" \n");
   scanf("%d",&students);	/* Data Input 1 (Number of Students) */
   printf(" \n");
   printf(" \n");
   while((students <1) || (students >60))	/* Validation Loop 1 (Number of Students Within Rage 1 - 60) */
   {	/* Validation Loop 1 Start */
      printf("Error 001 - Number Out of Range! \a");	/* Error Message With System Beep */
      printf(" \n");
      printf(" \n");
      printf("Please Input The Number of Students You Wish To Grade");
      printf(" \n");
      printf(" \n");
      scanf("%d",&students);	/* Data Input 1 (Number of Students) */
      printf(" \n");
      printf(" \n");
   }	/* Validation Loop 2 End */
}	/* Input Function End */

void process(void)
{	/* Process Function Start */
   for(count=1; count<=students; count++)	/* Loop 1 (Repeat The Following Code For Each Student) */
   {	/* Loop 1 Start */
      printf("Please Input Students First Name");
      printf(" \n");
      printf(" \n");
      scanf("%s",fname);	/* Data Input 2 (Students First Name) */
      printf(" \n");
      printf(" \n");
      printf("Please Input Students Surname");
      printf(" \n");
      printf(" \n");
      scanf("%s",sname);	/* Data Input 3 (Students Surname) */
      printf(" \n");
      printf(" \n");
      printf("Please Input Students Mark");
      printf(" \n");
      printf(" \n");
      scanf("%d",&mark);	/* Data Input 4 (Students Mark) */
      printf(" \n");
      printf(" \n");
      while((mark <0)||(mark >100))	/* Validation Loop 2 (Students Mark Within Range 0 - 100) */
      { /* Validation Loop 2 Start */
	 printf("Error 001 - Number Out of Range! \a");	/* Error Message With System Beep */
	 printf(" \n");
	 printf(" \n");
	 printf("Please Input Students Mark");
	 printf(" \n");
	 printf(" \n");
	 scanf("%d",&mark);	/* Data Input 4 (Students Mark) */
	 printf(" \n");
	 printf(" \n");
      }	/* Validation Loop 2 End */
      printf("Clearing Screen, One Moment Please...");
      sleep(1);	/* Program Pause (1 Second) */
      system("cls");	/* Clear Screen */
      printf("Students Results");
      printf(" \n");
      printf(" \n");
      printf("%s",fname);	/* Data Output 1 (Students First Name) */
      printf(" %s",sname);      /* Data Output 2 (Students Surname) */
      printf(" \n");
      printf(" \n");
      if(mark<40)	/* IF Statement 1 (Fail Grade) */
      { /* IF Statement 1 Start */
	 printf("GRADE: FAIL");
	 failcount++;	/* Increment The Fail Count */
      }	/* IF Statement 1 End */
      else
	 if(mark<65)	/* IF Statement 2 (Pass Grade) */
	 {	/* IF Statement 2 Start */
	    printf("GRADE: PASS");
	    passcount++;	/* Increment The Pass Count */
	 }	/* IF Statement 2 End */
	 else
	    if(mark<75)	/* IF Statement 3 (Merit Grade) */
	    {	/* IF Statement 3 Start */
	       printf("GRADE: MERIT");
	       meritcount++;	/* Increment The Merit Count */
	    }	/* IF Statement 3 End */
	    else	/* Final Else (Distinction Grade) */
	    {	/* Final Else Start */
	       printf("GRADE: DISTINCTION");
	       distinctioncount++;	/* Increment The Distinction Count */
	    }	/* Final Else End */
      total=total+mark;	/* Calculation To Determine The Total Value of All Marks */
      printf(" \n");
      printf(" \n");
      printf("Press Any Key To Continue");
      getch();	/* Wait For User To Press A Key */
      system("cls");
   }	/* Loop 1 End */
}	/* Process Function End */

void output(void)
{	/* Output Function Start */
   average=total/students;	/* Calculation To Determine The Average of All Marks */
   printf("Number of Students:	%d",students);	/* Data Output 3 (Number of Students) */
   printf(" \n");
   printf(" \n");
   printf("Average Mark:	   	   %.2f",average);	/* Data Output 4 (Average Grade) */
   printf(" \n");
   printf(" \n");
   printf("Number of Students Achieving The Following Grades");
   printf(" \n");
   printf(" \n");
   printf("Fail:		%d",failcount);	/* Data Output 5 (Students Achieving Fail) */
   printf(" \n");
   printf("Pass:		%d",passcount);	/* Data Output 6 (Students Achieving Pass) */
   printf(" \n");
   printf("Merit:		%d",meritcount);	/* Data Output 7 (Students Achieving Merit) */
   printf(" \n");
   printf("Distinction:	%d",distinctioncount);	/* Data Output 8 (Students Achieving Distinction) */
   printf(" \n");
   printf(" \n");
   printf(" \n");
   printf("Press Any Key To Exit");
   getch();	/* Wait For User To Press A Key */
}	/* Output Function End */

void intro(void)
{	/* Intro Function Start */
   printf("Archer Software Presents\n");
   printf("Grade Calculator\n");
   printf(" \n");
   printf("One Moment Please...");
   sleep(2);	/* Program Pause (2 Seconds) */
   printf(" \n");
   printf(" \n");
}	/* Intro Function End */

void clear(void)
{	/* Clear Function Start */
   printf(" \n");
   printf(" \n");
   printf("Clearing Screen, One Moment Please...");
   sleep(1);	/* Program Pause (1 Second) */
   system("cls");
}	/* Clear Function End */

void load(void)
{	/* Load Function Start */
   printf("Loading.");
   sleep(1);	/* Program Pause (1 Second) */
   printf(".");
   sleep(1);	/* Program Pause (1 Second) */
   printf(".");
   sleep(1);	/* Program Pause (1 Second) */
   printf(".");
   printf(" \n");
   printf(" \n");
}	/* Load Function End */

thnx

Do someting like:

Example

Code:

char line[256];

do {
  fgets(line, sizeof(line), stdin);
} while(sscanf(line, "%d", &students) != 1);

Next time cut your code down a bit for us bud. Oh and the above could use improvements such as telling the user that their input was invalid.

Also, I would refactor that code, its hard/annoying to read.

By the way, just to clarify part of my code, remember that the scanf() functions return how many requested items were successfully found. In the case of the string "%d" you are looking for a single integer. Which is why the do while loop ends as soon as only 1 item is found by sscanf().