CS208 Introduction to Computer Systems
Monday, 15 September 2025

+ Hi!
- Welcome back
- Jeff Ondich; call me Jeff; Olin 301A; jondich

+ Today
- Opening convo schedule, so only 50 minutes
- Minimal class logistics (more to come on Wednesday)
- hello.c
- bits & bytes

+ Meet the prefect

+ hello.c
- go to the samples page in a browser
- connect to mantis
- create hello.c and copy the code over
- gcc -Wall -Werror -g -o hello hello.c
- ./hello

+ bits and bytes
- what's a bit?
- what's a byte?
    why 8 bits in a byte?
    for character storage: A-Z, a-z, !@#$%^&&*(()_+..., 0-9,...
- computer memory is a list of bytes
    each byte in memory has an "address"

+ bitwise operators
         and  -  x & y
          or  -  x | y
         xor  -  x ^ y
         not  -  ~x
 shift left   -  x << n
 shift right  -  x >> n

how are they different from boolean operators &&, ||, !

+ Coming up next
- Friday assignment
- Lab on Wednesday
- Lots more C and Unix
- Integer notations: binary (0b), octal (0), decimal, hexadecimal (0x)
- Data representation: integers, characters, real numbers, strings