Tid-Bits C I/O

1 :
     char array[100];
    printf("%d" , scanf("%s" , arr));
    //input  : Jimmmy
    prints 1  as scan returns number of inputs successfully read
 2: 
    printf(" \"JIMMY %% N  %% JOLLY\"");
   
    output : "JIMMY % N % JOLLY"
   
    (\\\) backslash are used for escaping double quotes
   
 3: prototype of printf() in C :
              int printf(const char *format, ...);
 4:

    The stdout stream is buffered, so will only display what’s in the buffer after it reaches a newline (or when it’s told to)
    eg :
    printf(“\%\n”); prints : %
   
   
  5 :
    Use of backspace \b  and return  \r escape characters is terminal dependent :
        http://stackoverflow.com/questions/17236242/usage-of-b-and-r-in-c
       
   6:
        int main()
            {
               printf(1 + "Jjim");
               return 0;
            }
           
            prints : jim
          
           printf()  prototype as int printf( const char *format , ... ) ; The compiler adds 1 to base address of "Jjim" and sends "jim" as an arguemnts to
           printf() function defined in stdio.h header file .
    7:
            int main()
                {
                    printf("%c ", 5["jimmyjolly"]);
                    return 0;
                }
               
              prints : 'j'
       
          Compiler assumes   5["jimmyjolly"] as *(5 + "jimmyjolly") Adding 5 to base address of the string increments the pointer to point 'j'
                             Applying value-of opertaor gives 'j' as final result
            Same logic for  "jimmyjolly"[5] where  output is j
     
     
      8 :
             gets() can read a string with spaces but a normal scanf() with %s can not.
             gets() doesn't do any array bound testing and should not be used
             use fgets() instead :
                char *fgets(char *s, int n, FILE *stream);
                fgets read at most n-1 characters into the array s, stopping if a newline is encountered, the newline is included in the array, which is terminated by ‘\0'.
                fgets returns s, or NULL if end of file or error occurs.
     9 :
            #include <stdio.h>

            int main()
            {
                char str[50] = {0};
                scanf("%4s", str);
                printf(str);
                getchar();
                return 0;
            }
           
            input :  jimmy
            ouput : jimmy
           statment  scanf("%4s" , str ) ;  Read maximum 4 characters from console where str is a char array variable eg. char str[50];
          
          
        10 :
           
            printf(“%.*s”, n, s); in this statement value of pointer will move till nth character of s , printing n characters

            .* means The precision is not specified in the format string, but as an additional integer value argument preceding the argument that has to be formatted.
        11 :
             printf function returns the number of characters successfully printed on the screen.
         12 :
            The return type of getchar() is int to accommodate EOF which indicates failure
          13 :
             for a CPU with memory mapped I/O ,  I/O protection is ensured by operating system routine (s)