/*
    integers.c
    Jeff Ondich, 16 Jan 2023, originally named integers2.c
    Modified by Tanya Amert for Fall 2023

    How are integers specified?  What kinds of values do they have?

    Compile as usual:

        gcc -Wall -Werror -g -o integers integers.c

    Run with no command-line arguments:

        ./integers
*/
#include <stdio.h>
#include <stdlib.h> // atoi comes from here, and converts a null-terminated
                    // char array (a "C string") into a number

void print_usage_statement(const char *program_name);

// For each section: uncomment, predict output, try it.
int main(int argc, char *argv[])
{
    int j;

    if (argc != 2)
    {
        print_usage_statement(argv[0]);
    }

    // Run exactly one section using a switch statement
    // (note the break; lines)
    int section = atoi(argv[1]);
    switch (section)
    {
        case 1:
            fprintf(stdout, "== SECTION 1: fprintf output specifiers ==\n");
            j = 165;
            fprintf(stdout, "Decimal: %d\n", j);
            fprintf(stdout, "Hexadecimal (lower case): 0x%x\n", j);
            fprintf(stdout, "Hexadecimal (upper case): 0x%X\n", j);
            fprintf(stdout, "Octal: %o\n", j);
            break;
        case 2:
            fprintf(stdout, "== SECTION 2: specifying an integer in binary ==\n");
            j = 0b10100101;
            fprintf(stdout, "Decimal: %d\n", j);
            fprintf(stdout, "Hexadecimal: 0x%X\n", j);
            break;
        case 3:
            fprintf(stdout, "== SECTION 3: specifying an integer in hexadecimal ==\n");
            j = 0xA5;
            fprintf(stdout, "Decimal: %d\n", j);
            fprintf(stdout, "Hexadecimal: 0x%X\n", j);
            break;
        case 4:
            fprintf(stdout, "== SECTION 4: what is going on here?!? ==\n");
            j = 0254;
            fprintf(stdout, "Decimal: %d\n", j);
            fprintf(stdout, "Hexadecimal: 0x%X\n", j);
            fprintf(stdout, "Octal: %o\n", j);
            break;
        case 5:
            fprintf(stdout, "== SECTION 5: specifying a peculiar hex value ==\n");
            j = 0xFFFFFFFE;
            fprintf(stdout, "Hexadecimal: 0x%X\n", j);
            fprintf(stdout, "Decimal: %d\n", j);
            break;
        case 6:
            fprintf(stdout, "== SECTION 6: isn't this an infinite loop? ==\n");
            j = 1;
            while (j > 0)
            {
                j++;
            }
            fprintf(stdout, "We made it! j = %d\n", j);
            /* What happened? Why does j have the value it has? */
            break;
        default:
            fprintf(stderr, "You need to specify section_num between 1 and 6, inclusive.\n");
            break;
    }

    return 0;
}

// Prints information for how to use this program.
void print_usage_statement(const char *program_name)
{
    fprintf(stderr, "Usage: %s section_num\n", program_name);
    fprintf(stderr, "  shows different ways to specify/use integers,\n");
    fprintf(stderr, "  where section_num is an integer from 1 to 6, inclusive\n");
}