L1: Administrative Details
Notes
- C
- Assambly
- C++
- Concurrent Programming
- Scheme
- Python
C is more procedure-oriented, from main to sub function, and sub function to sub-sub function. “Procedure Paradiam”
Concurrent programming issue: The shared resource that two different processes to access to.
Scheme is in functional paradiam: rely on a return from a function to move forward! Thus you can program without side effects.
e.g. side effects in C/C++: Pass a data structure into a function by reference, and change it in the function, when return, it changed.
Python, with good web libraries.
Qustions
- Here talking about concurrent programming in one CPU? Seemingly in a Time-sharing system.
Glossary
handouts 讲义 mileage 里程 pertinent 相关的 synopsis 概要 assembly code 汇编代码
asterisks 星号 ampersands 连字号 miniature 微型
L2: C/C++ Data Types - Interpretations
Notes
Low-level memory mechanisms.
C/C++ Data types |Data Type|Length| |—-|—-| |bool|1 byte| |char|1 byte| |short|2 byte| |int|4 byte*| |long|4 byte| |float|4 byte| |double|8 byte|
Technically, a Boolean can be mapped by a single bit in memory. Can engineer the compiler to do so.
Considering sign, the first bit in 1 — minus sign.
When 0000 0000 0000 0111 + 1000 0000 0000 0111, if the first bit is sign, the result is not right. To deal with this problem, use invert + 1 to represent negative values. Two’s complement(补码)
char ch = 'A';
short s = ch;
cout << s << endl;
OUTPUT:
65
ch 1111 65 s 1111 65
int i = 2^21+2^10+2^1
short s = i
OUTPUT:
1026
short s = -1;
int i = s;
s 1111 1111 1111 1111 i 1111 1111 1111 1111 1111 1111 1111 1111
Floating things are wierd. See IEEE 754
Single (32 bits/ 4 bytes):
(-1)^sign(1.b22b21…b0)2^(e-127)
Double (64 bits/8 bytes):
Qustions
Precision varies with the magnitude of the represented number:
Single Precision: 10^N~10e(N-8) Double Precision: 10^N-10e(N-16)
int i =5;
float f=i;
cout<<f<<endl;
5=>5.0=1.25*2^e # Totally different!
Be careful with the precision loss when convert int to float!
Double makes things better, merely better.
Glossary
Updated 2020-04-26