CS208 Introduction to Computer Systems
Monday, 12 January 2026

+ Quiz

+ Questions?

+ Today
- Negative integers
- Last week's quiz returned
- Start on character encodings

+ Coming up
- Assignment due Thursday
- Quiz Friday (two's complement integers)
- Assignment due Sunday

+ Negative integers
- Signed magnitude
- Two's complement
- Why two's complement?
- Negating in two's complement

Question: assuming the following is a 32-bit two's complement representation of an integer, what is its decimal value?

    0xFFFFFFE5

+ Quizzes back

+ Character encoding
- What?
- ASCII
- ISO-8859-1

====
def factorial(n):
    total = 1
    for k in range(2, n+1):
        total *= k
    return total

for k in range(1, 21):
    print(f'{k}! = {factorial(k)}')

---

#include <stdio.h>

int factorial(int n) {
    int total = 1;
    for (int k=2; k <= n; k++) {
        total *= k;
    }
    return total;
}

int main() {
    for (int k=1; k <= 20; k++) {
        printf("%d! = %d\n", k, factorial(k));
    }
    return 0;
}

---

#include <stdio.h>

int main() {
    int k = 1;
    while (k > 0) {
        k++;
    }
    printf("%d\n", k);
    printf("0x%x\n", k);

    return 0;
}

---

#include <stdio.h>

int main() {
    int x = 0xFFFFFFE5;
    printf("%d\n", x);

    x = (~x) + 1;
    printf("%d\n", x);

    return 0;
}