Write program to find and replace the character in the word - c

Question

Program question is:
Write a C program to find and replace the character in the word.
Here flag('A'/'F') indicates whether all occurrences has to be replaced or only the first occurrence has to be replaced.
I have written this code
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
void cond(char *a,int n,char k,char l,char m)
{
printf("The word is\n");
int i,count=0,max=0;
switch(m)
{
case 'A':
for(i=0;i<n;i++)
{
if(a[i]==k)
{
a[i]=l;
count++;
}
}
if(count==0)
{
printf("No such character present in the word.");
}
else
for(i=0;i<n;i++)
{
printf("%c",a[i]);
}
break;
case 'F':
for(i=0;i<n;i++)
{
while(max<1)
{
if(a[i]==k)
{
a[i]=l;
max++;
}
}
}
if(max==0)
{
printf("No such character present in the word.");
}
else
for(i=0;i<n;i++)
{
printf("%c",a[i]);
}
break;
}
}
int main()
{
char a[20],b,e,p;
printf("Enter the word:\n");
scanf("%s",a);
printf("Enter the character to be find:\n");
scanf("%c\n",&b);
printf("Enter the character to be replaced:\n");
scanf("%c\n",&e);
printf("Enter the 'A'/'F':\n");
scanf("%c\n",&p);
int n=strlen(a);
cond(a,n,b,e,p);
return 0;
}
It does not give any output
For example:
If I input this
Enter the word: aeroplane
Enter the character to be find:a
Enter the character to be replaced:z
Enter the 'A'/'F': A
The word is
It gives a blank output
someone, please help me for this code.

Answer 1

Since a is of type char*, a[i] is a char. k is a char too, thus you can simply compare them like this:
if(a[i] == k)
Moreover your scnafs' use the newline, discard it. Change this:
scanf("%c\n",&b);
to this:
scanf(" %c",&b);
where you should notice I left a space before %c, in order to eat a pending character (I have an example here).

Answer 2

If you test your functions it is better to create some test cases and avoid user input. This can be added later when you are sure that your function works.
Example (I do not know what n means in your example as you even do not declare it in your main :)
int s_replace(char *haystack, char needle, char replace, char flag) // a/A only first - any other complete
{
int result = 0;
if (haystack == NULL) result = -1;
if (!result)
{
while (*haystack)
{
if (*haystack == needle)
{
*haystack = replace;
if (!(result++) && tolower(flag) == 'a')
{
break;
}
}
haystack++;
}
}
return result;
}
int main()
{
int result;
char test[] = "Program question is: Write a C program to find and replace the character in the word. Here flag('A'/'F') indicates whether all occurrences has to be replaced or only the first occurrence has to be replaced.";
printf("Original string = \"%s\"\n", test);
result = s_replace(test, 'a', 'z', 'A');
switch (result)
{
case -1:
printf("Error !!!!!\n");
break;
case 0:
printf("Nothing was found. \n");
break;
default:
printf("Amended string = \"%s\"\n", test);
printf("Number of changes - %d\n", result);
}
return 0;
}