Computer Systems Fundamentals

#include <stdio.h>
#include <limits.h>

int main(void) {

    char c;
    signed char sc;
    unsigned char uc;
    short s;
    unsigned short us;
    int i;
    unsigned int ui;
    long l;
    unsigned long ul;
    long long ll;
    unsigned long long ull;

    printf("%18s %5s %4s\n", "Type", "Bytes", "Bits");
    printf("%18s %5lu %4lu\n", "char", sizeof c, 8 * sizeof c);
    printf("%18s %5lu %4lu\n", "signed char", sizeof sc, 8 * sizeof sc);
    printf("%18s %5lu %4lu\n", "unsigned char", sizeof uc, 8 * sizeof uc);

    printf("%18s %5lu %4lu\n", "short", sizeof s, 8 * sizeof s);
    printf("%18s %5lu %4lu\n", "unsigned short", sizeof us, 8 * sizeof us);

    printf("%18s %5lu %4lu\n", "int", sizeof i, 8 * sizeof i);
    printf("%18s %5lu %4lu\n", "unsigned int", sizeof ui, 8 * sizeof ui);

    printf("%18s %5lu %4lu\n", "long", sizeof l, 8 * sizeof l);
    printf("%18s %5lu %4lu\n", "unsigned long", sizeof ul, 8 * sizeof ul);

    printf("%18s %5lu %4lu\n", "long long", sizeof ll, 8 * sizeof ll);
    printf("%18s %5lu %4lu\n", "unsigned long long", sizeof ull, 8 * sizeof ull);

    printf("\n%18s %20s %20s\n", "Type", "Min", "Max");
    printf("%18s %20d %20d\n", "char", CHAR_MIN, CHAR_MAX);
    printf("%18s %20d %20d\n", "signed char", SCHAR_MIN, SCHAR_MAX);
    printf("%18s %20d %20d\n", "unsigned char", 0, UCHAR_MAX);

    printf("%18s %20d %20d\n", "short", SHRT_MIN, SHRT_MAX);
    printf("%18s %20d %20d\n", "unsigned short", 0, USHRT_MAX);

    printf("%18s %20d %20d\n", "int", INT_MIN, INT_MAX);
    printf("%18s %20d %20d\n", "unsigned int", 0, UINT_MAX);

    printf("%18s %20ld %20ld\n", "long", LONG_MIN, LONG_MAX);
    printf("%18s %20d %20lu\n", "unsigned long", 0, ULONG_MAX);

    printf("%18s %20lld %20lld\n", "long long", LLONG_MIN, LLONG_MAX);
    printf("%18s %20d %20llu\n", "unsigned long long", 0, ULLONG_MAX);

    return 0;
}

#include <stdint.h>

int main(void) {

                 // range of values for type
                 //             minimum               maximum
    int8_t   i1; //                 -128                  127
    uint8_t  i2; //                    0                  255
    int16_t  i3; //               -32768                32767
    uint16_t i4; //                    0                65535
    int32_t  i5; //          -2147483648           2147483647
    uint32_t i6; //                    0           4294967295
    int64_t  i7; // -9223372036854775808  9223372036854775807
    uint64_t i8; //                    0 18446744073709551615

    return 0;
}

#include <stdio.h>

int main(void) {

    // Common C bug:

    char c;  // c should be declared int
    while ((c = getchar()) != EOF) {
        putchar(c);
    }

    // Typically `stdio.h` contains:
    // ```c
    // #define EOF -1
    // ```
    //
    // - most platforms: char is signed (-128..127)
    //   - loop will incorrectly exit for a byte containing 0xFF
    //
    // - rare platforms: char is unsigned (0..255)
    //   - loop will never exit

    return 0;
}

// header file so we use print_bits in several examples
#ifndef PRINT_BITS_H
#define PRINT_BITS_H

#include <stdint.h>
void print_bits(uint64_t value, int how_many_bits);

#endif

#include <stdio.h>
#include <stdint.h>

#include "print_bits.h"

// extract the nth bit from a value
int get_nth_bit(uint64_t value, int n) {
    // shift the bit right n bits
    // this leaves the n-th bit as the least significant bit
    uint64_t shifted_value = value >> n;

    // zero all bits except the the least significant bit
    int bit = shifted_value & 1;

    return bit;
}

// print the bottom how_many_bits bits of value
void print_bits(uint64_t value, int how_many_bits) {
    // print bits from most significant to least significant

    for (int i = how_many_bits - 1; i >= 0; i--) {
        int bit = get_nth_bit(value, i);
        printf("%d", bit);
    }
}

#include <stdio.h>
#include <stdint.h>
#include "print_bits.h"

int main(void) {
    int a = 0;
    printf("Enter an int: ");
    scanf("%d", &a);

    // sizeof returns number of bytes, a byte has 8 bits
    int n_bits = 8 * sizeof a;

    print_bits(a, n_bits);
    printf("\n");

    return 0;
}

#include <stdio.h>
#include <stdint.h>
#include "print_bits.h"

int main(void) {

    for (int i = -128; i < 128; i++) {
        printf("%4d ", i);
        print_bits(i, 8);
        printf("\n");
    }

    return 0;
}