## Computer Science 237 |

**Lecture 03: Binary Arithmetic, Signed Representations****Date: September 13, 2006**

* *

- Announcements
- Not CS, but potentially interesting talk tonight: Shuttle astronaut Stephanie Wilson, Brooks-Rogers, 7 PM.
- My office hours on Friday may start and end early. Come by if you need help!

- Lab continues - ask questions when stuck
- Thrown into the deep end and don't know how to swim?
- You will soon know what I'm talking about on pages 1 and 2. If not today, then Friday, I promise.
- Suggestion: avoid the
`sqrt`function, in fact avoid the math library altogether - Useful C functions:
`atoi(3)`,`scanf(3)`. - Useful C ideas: bit shifts and logical operators.
- Useful C example:
`show_bytes`from last time. - TA hours Sunday evening in TCL 312. I hope to be around some then, too.

- Memory model and pointers
- Know your prefixes: Kilo, Mega, Giga, Tera, Peta, Exa, Zetta, Yotta
- Just think of memory as a big array of bytes.
- A pointer? Just a memory location whose contents is a memory location.

- Strings and arrays
- no
`String`s in C - just use an array of`char`.

- no
- Math
- unsigned addition and multiplication
- signed integer representations
- signed magnitude
- Excess N
- 1's complement
- 2's complement

- signed addition