// Andrew Taylor - andrewt@unsw.edu.au // 08/06/2020 // Print an integer in hexadecimal without using printf // to demonstrate using bitwise operators to extract digits /*``` \$ dcc print_int_in_hex.c -o print_int_in_hex \$ ./print_int_in_hex Enter a positive int: 42 42 = 0x0000002A \$ ./print_int_in_hex Enter a positive int: 65535 65535 = 0x0000FFFF \$ ./print_int_in_hex Enter a positive int: 3735928559 3735928559 = 0xDEADBEEF \$ ```*/ #include #include void print_hex(uint32_t n); int main(void) { uint32_t a = 0; printf("Enter a positive int: "); scanf("%u", &a); printf("%u = 0x", a); print_hex(a); printf("\n"); return 0; } // print n in hexadecimal void print_hex(uint32_t n) { // sizeof returns number of bytes in n's representation // each byte is 2 hexadecimal digits int n_hex_digits = 2 * (sizeof n); // print hex digits from most significant to least significant for (int which_digit = n_hex_digits - 1; which_digit >= 0; which_digit--) { // shift value across so hex digit we want // is in bottom 4 bits int bit_shift = 4 * (n_hex_digits - which_digit - 1); uint32_t shifted_value = n >> bit_shift; // mask off (zero) all bits but the bottom 4 bites int hex_digit = shifted_value & 0xF; // hex digit will be a value 0..15 // obtain the corresponding ASCII value // "0123456789ABCDEF" is a char array // containing the appropriate ASCII values (+ a '\0') int hex_digit_ascii = "0123456789ABCDEF"[hex_digit]; putchar(hex_digit_ascii); } }