how to convert char to int in c?

Question

I was trying to make a program which was to much big for a noob like. it was approximatly 100 line(for noob like me,its big).But every time i run its loops aren't ending.So dicided to compile and check small parts of the code and I get bingo in fist part.here is that part

#include <stdio.h>
int main(){//B main
    int cha,z; 
    printf("enter the alphabte in capital until you want the alphabats :-  ");
    scanf("%c",&z);
    for(;z>=65;z--)
        for(cha=65;cha<=z;cha++)
        {  
            if(cha!=z)
                printf("%c ",cha);
            else
                printf("%c \n",cha);
        }
}//B main

.I have modified it it and if i enter c it should give an output like this:-

A B C
A B
A

But the loop does not ends and i keep getting something like this on terminal

              ! " # $ % & ' ( ) * + , - . / 0 1 2 3 4 5 6 7 8 9 : ; < = > ? @ A B C D E F G H I J K L M N O P Q R S T U V W X Y Z [ \ ] ^ _ ` a b c d e f g h i j k l m n o p q r s t u v w x y z { | } ~  � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �        

thus try this part

 #include <stdio.h>
 int main(){
     int a;
     scanf("%d",&a);
     printf("%d",a);
 }

If I enter A then it should give me 65 as an output as A's ASCII value is 65 but it gives me following output

32766

but my this program give me correct ASCII values

  #include <stdio.h>
  #include <stdlib.h>

  int main(){
      int b,c;
      b=0;
      printf("\n these are ASCII values of all letters \n\n\n ");
      while(b<=255)
      {
           printf("%c %d \n",b,b);
           b=b+1;
      }
 }

How can I use characters like a A G j as integers with there ASCII values?

How can I do arithmetic operations with their ASCII values?

Answer 1

First of all, your second code should be:

#include <stdio.h>

int main(){
       char a;
       scanf("%c", &a); // read in single character value
       printf("%d",a); 
 }

Some other notes:

• You can use literal chars instead of the values in your code:
  if (char == 'A'){ printf("char is 'A'");}
• You can add and subtract like normal values:
  printf("%d", 'C' - 'A'); prints 2
• I just ran your first code snippet. It works fine for me.

This is the output:

$ ./a.exe
enter the alphabte in capital until you want the alphabats :-  C
A B C
A B
A

Answer 2

In your example, change it to use %c:

#include <stdio.h>
int main()
{
  char a;
  scanf("%c",&a);
  printf("%d",a);
}

Put in 'A' and it prints 65 as expected.

Now just expand that for your code. Oh and check the return value of scanf. I didn't here because I wanted to keep the example simple, but always do it in actual code.

Answer 3

Provide your own set of valid characters.
Use strchr to see if the input is in the set of valid characters. If not, try again for correct input.
Once correct input is obtained, use strchr again to make sure the incremented and decremented values remain valid.

#include <stdio.h>
#include <string.h>

int main( void) {
    char valid[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    char z = valid[0];
    char cha = valid[0];
    char *ok = NULL;
    char *chaok = NULL;

    printf("enter the alphabte in capital until you want the alphabats :-  ");
    do {
        if ( 1 != scanf(" %c",&z)) {
            fprintf ( stderr, "problem with input\n");
            return 0;
        }
        ok = strchr ( valid, z);
        if ( !ok) {
            printf ( "enter an uppercase letter. try again\n");
        }
    } while ( !ok);

    while ( ( ok = strchr ( valid, z)) && ok >= valid) {
        cha = valid[0];
        while ( ( chaok = strchr ( valid, cha)) && chaok <= ok) {
            if( chaok != ok)
                printf("%c ",cha);
            else
                printf("%c \n",cha);
            cha = *(++chaok);
        }
        z = 0x1;
        if ( ok > valid) {
            z = *(ok - 1);
        }
    }
}