looping a program that converts to uppercase and shifts 4 letter grades in C -

this program calls 2 functions uppercase(), converts input uppercase, , shift(), shifts grade input.

here's uppercase() function:

void uppercase(char *p) {   if(islower(*p)) {     *p = toupper(*p);     }  } 

here's shift() function:

void shift(char *p1, char *p2, char *p3, char *p4) {  int count = 0;  {  ++count;  char tmp;  tmp = *p4;  *p4 = *p3;  *p3 = *p2;  *p2 = *p1;  *p1 = tmp;  printf("grades shifted #%i:   %c %c %c %c \n", count, *p1, *p2, *p3, *p4);  } while (count < 4);  } 

here's main function.

#include <stdio.h> #include <ctype.h> main (void) {  float choice;   {  char c1, c2, c3, c4;  printf ("enter 4 letter grades find statistics: ");  scanf("%c %c %c %c", &c1, &c2, &c3, &c4);  getchar();   uppercase(&c1);  uppercase(&c2);  uppercase(&c3);  uppercase(&c4);   printf("input grades: %c %c %c %c\n", c1, c2, c3, c4);  shift(&c1, &c2, &c3, &c4);  printf("want shift more grades (y/n)? ");  choice = getchar();      } while ( choice == 'y' || choice == 'y'); getchar();  } 

my output looks this

enter 4 letter grades find statistics: abcd
input grades: b c d
grades shifted #1: d b c
grades shifted #2: c d b
grades shifted #3: b c d a
grades shifted #4: b c d
want shift more grades (y/n)? y
enter 4 letter grades find statistics: adff
input grades:
d f
grades shifted #1: f
d
grades shifted #2: d f
a
grades shifted #3: d f
grades shifted #4:
d f
want shift more grades (y/n)?

the format gets messed on second input, , when input y after second input, program closes. i've been tinkering past hour , can't figure out why formatting gets messed or why loop closes/crashes on third attempt.

also how can make main function accepts inputs of a-d or f.

thanks.

i think it's because have new line sitting in getchar() input

when enter 'y' press enter, you're getting "y\n".

clear input when re-entering while loop

printf("want shift more grades (y/n)? "); choice = getchar(); c = getchar(); while (c != '\n' && c != eof)   c = getchar(); } while ( choice == 'y' || choice == 'y'); 

for second question:

you need check values of c1,c2,c3,c4 luckily there's function that

while( !(isalpha(c1) && isalpha(c2) && isalpha(c3) && isalpha(c4)) )   printf ("enter 4 letter grades find statistics: ");   scanf("%c %c %c %c", &c1, &c2, &c3, &c4);   getchar(); 

note isalpha function checks value of each character... here's ascii table, notice a-z , a-z are. http://www.asciitable.com/

---

scanf/getchar() line clearing: http://www.velocityreviews.com/forums/t318260-peek-at-stdin-flush-stdin.html