Error in using strcpy [duplicate] - c

Question

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What header should I include for memcpy and realloc?
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warning: incompatible implicit declaration of built-in function 'strlen' and 'strcpy' [duplicate]
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Closed 5 years ago.
#include<stdio.h>
struct stud
{
char name[20];
int mark;
int per;
char grad[5];
};
void main(){
int i,n;
printf("Enter number of students");
scanf("%d",&n);
struct stud s[n];
for(i=1;i<=n;i++)
{
printf("Enter name of student");
scanf("%d",s[i].name);
printf("Enter obtained marks");
scanf("%d",&s[i].mark);
s[i].per=s[i].mark/5;
}
for(i=1;i<=n;i++)
{
if(s[i].per>=80)
strcpy(s[i].grad,"A");
else if(s[i].per>=60)
strcpy(s[i].grad,"B");
else if(s[i].per>=50)
strcpy(s[i].grad,"C");
else if(s[i].per>=40)
strcpy(s[i].grad,"D");
else
strcpy(s[i].grad,"F");
}
for(i=1;i<=n;i++)
{
printf("&s",s[i].name);
printf("&d",s[i].mark);
printf("&d",s[i].per);
printf("&s",s[i].grad);
}
}
When executing this code it's showing error :
main.c: In function ‘main’:
main.c:25:10: warning: implicit declaration of function ‘strcpy’ [-Wimplicit-function-declaration]
strcpy(s[i].grad,"A");
^~~~~~
main.c:25:10: warning: incompatible implicit declaration of built-in function ‘strcpy’
main.c:25:10: note: include ‘<string.h>’ or provide a declaration of ‘strcpy’
main.c:27:11: warning: incompatible implicit declaration of built-in function ‘strcpy’
strcpy(s[i].grad,"B");
^~~~~~
main.c:27:11: note: include ‘<string.h>’ or provide a declaration of ‘strcpy’
main.c:29:11: warning: incompatible implicit declaration of built-in function ‘strcpy’
strcpy(s[i].grad,"C");
^~~~~~
main.c:29:11: note: include ‘<string.h>’ or provide a declaration of ‘strcpy’
main.c:31:10: warning: incompatible implicit declaration of built-in function ‘strcpy’
strcpy(s[i].grad,"D");
^~~~~~
main.c:31:10: note: include ‘<string.h>’ or provide a declaration of ‘strcpy’
main.c:33:10: warning: incompatible implicit declaration of built-in function ‘strcpy’
strcpy(s[i].grad,"F");
^~~~~~
main.c:33:10: note: include ‘<string.h>’ or provide a declaration of ‘strcpy’
What's the error here ?

Answer 1

scanf("%d",s[i].name); is undefined behavior. It will be "%s" format specifier.
And printf("%s",s[i].name) not &s.
Include string.h header file.
Also array index out of bound while getting input. Also undefined behavior. Array indices start from 0. All loop would be for(i=0;i<=n-1;i++)
and include header like this:
#include <string.h>
for(i=0;i<=n-1;i++)
{
printf("Enter name of student");
scanf("%s",s[i].name);
printf("Enter obtained marks");
scanf("%d",&s[i].mark);
s[i].per=s[i].mark/5;
}
Another change
for(i=1;i<=n;i++)
{
printf("%s",s[i].name);
printf("%d",s[i].mark);
printf("%d",s[i].per);
printf("%s",s[i].grad);
}