program for calculation

[tommytmh]

#include <stdio.h>
#include <string.h>
int add(int a, int b){
 int ans;
 ans=a+b;
 return ans;
}
int mul(int a, int b){
 int ans;
 ans=a*b;
 return ans;
}
int sub(int a, int b){
 int ans;
 ans=a-b;
 return ans;
}
int div(int a, int b){
 int ans;
 ans=a/b;
 return ans;
}
void main(){
 char choice[20];
 int ans;
 int a,b;
 scanf("%s",&choice);
 if(choice=="add")
 {
  scanf("%d %d",&a,&b);
  ans=add(a,b);
  printf("%d",ans);
 }
 else if(choice=="sub")
 {
  scanf("%d %d",&a,&b);
  ans=sub(a,b);
  printf("%d",ans);
 }
 else if(choice=="mul")
 {
  scanf("%d %d",&a,&b);
  ans=mul(a,b);
  printf("%d",ans);
 }
 else if(choice=="div")
 {
  scanf("%d %d",&a,&b);
  ans=div(a,b);
  printf("%d",ans);
 }
 else
  printf("Wrong input");
}

i don't know what the problem is.thanks for help

[CommonTater]

The first problem is that you didn't bother to indent and space your code in any meaningful way.

The second problem is that you cannot compare strings across the == sign in C. C doesn't know about strings, so you have to use library functions such as strcmp() to do these things.

[tommytmh]

Thanks for you help but i don't know how to use strcmp() to do it. i know the function of strcmp() which is used to comparing the number of char in the strings. can you give me some ideas?

[manasij7479]

Thanks for you help but i don't know how to use strcmp() to do it. i know the function of strcmp() which is used to comparing the number of char in the strings. can you give me some ideas?

strcmp

[chibi.coder]

#include <stdio.h>
#include <string.h>
int add(int a, int b){
 int ans;
 ans=a+b;
 return ans;
}
int mul(int a, int b){
 int ans;
 ans=a*b;
 return ans;
}
int sub(int a, int b){
 int ans;
 ans=a-b;
 return ans;
}
int div(int a, int b){
 int ans;
 ans=a/b;
 return ans;
}
void main(){
 char choice[20];
 int ans;
 int a,b;
 scanf("%s",&choice);
 if(choice=="add")
 {
  scanf("%d %d",&a,&b);
  ans=add(a,b);
  printf("%d",ans);
 }
 else if(choice=="sub")
 {
  scanf("%d %d",&a,&b);
  ans=sub(a,b);
  printf("%d",ans);
 }
 else if(choice=="mul")
 {
  scanf("%d %d",&a,&b);
  ans=mul(a,b);
  printf("%d",ans);
 }
 else if(choice=="div")
 {
  scanf("%d %d",&a,&b);
  ans=div(a,b);
  printf("%d",ans);
 }
 else
  printf("Wrong input");
}

i don't know what the problem is.thanks for help

Use strcmp() for comparing strings.
You are comparing addresses of the strings instead of strings.

[tommytmh]

#include <stdio.h>
#include <string.h>
int add(int a, int b){
 int ans;
 ans=a+b;
 return ans;
}
int mul(int a, int b){
 int ans;
 ans=a*b;
 return ans;
}
int sub(int a, int b){
 int ans;
 ans=a-b;
 return ans;
}
int div(int a, int b){
 int ans;
 ans=a/b;
 return ans;
}
void main(){
 char choice[20];
 char addd[20]="add",subb[20]="sub",mull[20]="mul",divv[20]="div";
 int ans;
 int a,b;
 scanf("%s",&choice);
 if(strcmp(choice,add)==0)
 {
  scanf("%d %d",&a,&b);
  ans=add(a,b);
  printf("%d",ans);
 }

Do you mean by this?Thanks

[CommonTater]

Thanks for you help but i don't know how to use strcmp() to do it. i know the function of strcmp() which is used to comparing the number of char in the strings. can you give me some ideas?

Yep... look up strcmp() in your compiler's library documentation. (If you don't have it get it.)

There you will find a full description of what it does, what it returns and which headers and libraries you need to use it.

[CommonTater]

Like this...

 scanf("%s",&choice);
 if(strcmp(choice,"add") == 0)
 {
  printf("Enter numbers to add : "); 
  scanf("%d %d",&a,&b);
  ans=add(a,b);
  printf("%d",ans);
 }

You don't need an array of strings, just compare to the string literal.

Again... you need to look this stuff up in your compiler's library documentation.

[tommytmh]

i've checked the library. if the two strings are exactly equal to each other , it will return 0. Thank you for help