CPS118. Lesson 1b: Computer Systems and Program Development. Objectives. What Is a Computer? What is an algorithm? Computer Components Binary number system Software Development Method problem solving. Computer Systems.
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3 types of computer systems:
CPU Registers: Only a few cells on CPU
Main memory (RAM): Millions of cells on circuits separate from CPU.
Secondary storage: Billions of cells on disks or tapes.
Secondary storage is not volatile.
Bit: Binary digit (0 or 1).
Byte: A group of 8 bits. One character.
Word: The width of a memory cell.
Each byte of main memory has an address.
All numbers are represented in binary.
All numbers are converted in binary:
ex: 9 = 1001
In a computer system, the leftmost bit is the sign bit (0 is positive, 1 is negative).
So 9 in a 32 bit system would be:
Real numbers in binary are expressed with a mantissa, a base and an exponent.
For a real number , the mantissa is defined as the positivefractional part
Suppose 9.0 in binary:
In 32 bits a simple view is
base and exponent=16 (base=2, exponent=4).
for 32 bit float number (8: exp, 23 mantissa):
0 00000100 10010000000000000000000
A double number is expressed in 64 bits:
52 bits for the mantissa, 11 bits for the exponent and 1 sign bit.
Exponent: right to left, like an integer.
Mantissa: left to right, 0.5, 0.25, 0.125, 0.0625,... and so on. 1 if needed, 0 if not.
So 9.0 is:
Characters are expressed using the ASCII code:
A = 65 = 01000001
g = 103 = 01100111
$ = 36 = 00100100
+ = 43 = 00101011
See code here:
Generation 1: Machine languages (pure binary)
Generation 2: Assembly languages (mnemonic codes)
Generation 3: High-Level Languages (C, Fortran, Java)
1. Define the problem
2. Analyse the problem.
3. Design a solution.
4. Implement the solution.
5. Test the program.
6. Update and maintain the program.
Here is a detail of step #4, implementation (actual programming):
4.1 Write the program source.
4.2 Compile the source code and check for errors.
4.3 Link the code with libraries and build the program.
4.4 Run the program.
1. It is portable.
2. It is efficient.
3. It is easy to learn.
4. It is modular.
5. It is widespread.