Computers and Programming

Chapter 1

Only the first two weeks contain theses slide-based videos. After that, you will see more demonstration videos and resources.

This looks like a lot of videos, but each video is not very long (about 55 minutes total).

What is a computer?

• One that computes (makes calculations).

• A programmable computer is an electronic device that:

  1. Retrieves numerical data
  2. Stores numerical data
  3. Performs arithmetic or logical operations on numerical data
  4. Outputs numerical data

NACA (NASA) - Dryden Flight Research Center “Computer Room” (1949)

Hardware

• Input devices feed data and programs into computers
  • Keyboard
  • Mouse
• Output devices display results
  • Monitor
  • Printer
  • Network Interface Card (NIC) (input/output)
• Central Processing Unit (CPU)
  • Brain of the computer
  • Usually, the most expensive piece of hardware
  • Carries out arithmetic and logical operations
  • Commonly a single chip called a microprocessor.
• Main memory (RAM)
  • Main memory is an ordered sequence of memory cells.
    • Each cell has a unique location in main memory, called the address of the cell
    • Also called primary storage or physical memory
  • Each cell can contain either a programming instruction or data.
• Secondary storage: device that stores information permanently
  • Hard drives
  • Flash drives
  • CDs
  • Tapes

Software

Software: programs that do specific tasks. There are two types of software.

1. System programs control the computer.
   • Operating system monitors the overall activity of the computer and provides services such as:
     • Memory management
     • Input/output activities
     • Storage management
2. Applications perform a specific task. For example,
   • Word processors
   • Web browsers
   • Games

What does a computer understand?

The language of computers.

Two Types of Signals

1. Analog signals: continuous wave forms
2. Digital signals: sequences including only a finite set of values (generally only 0s and 1s, which is call Binary).

Examples of Analog and Digital Signals

Binary

• Machine language: language of a computer a binary sequence (0s and 1s).
• Binary digit (bit): the digit 0 or 1
• Binary code (binary number): a sequence of 0s and 1s

Decimal	0	1	2	3	4	5	6	7	8	9
Binary	0	1	10	11	100	101	110	111	1000	1001

• Bit: A binary unit (can be either 0 or 1)
• Byte: A sequence of eight bits
• Kilobyte (KB): 210 bytes = 1024 bytes
• ASCII (American Standard Code for Information Interchange)
  • 128 characters
  • A is encoded as 01000001 (65th ASCII character)
  • 3 is encoded as 00110011 (51st ASCII character)

Unit	Symbol	Size		Size in Bytes	Size in Bytes
Byte		8 bits			1
Kilobyte	KB	bytes			1024
Megabyte	MB	KB	1024 KB		1,048,576
Gigabyte	GB	MB	1024 MB		1,073,741,824
Terabyte	TB	GB	1024 GB		1,099,511,627,776
Petabyte	PB	TB	1024 TB		1125899,906,842,624
Exabyte	EB	PB	1024 PB		1,152,921,504,606,846,976
Zettabyte	ZB	EB	1024 EB		1,180,591,620,717,411,303,424
Yottabyte	YB	ZB	1024 ZB		1,208,925,819,614,629,174,706,176

The Evolution of Programming Languages

• Early programmed written in machine language
• To calculate wages = rate × hours, where the rate is 20 and wages is 40 in machine language:

Machine Code	Purpose
11000111 01000101 11111100 00010100	Set rate to 20
11000111 01000101 11111000 00101000	Set hours to 40
00000000 10001011 01000101 11111100	Move the rate for multiplication
00001111 10101111 01000101 11111000	Multiply the rate by the hours
00000000 10001001 01000101 11110100	Store the results in wages

Using assembly language instructions,
rate = 20
hours = 40
wages = rate × hours
can be written as:

Assembly Code	Purpose
mov 20, ecx	Set rate to 20
mov 40, edx	Set hours to 40
mov eax, ecx	Move the rate for multiplication
imul eax, edx	Multiply the rate by the hours
mov DWORD PTR [r8], eax	Store the results in wages

• High-level languages include FORTRAN, COBOL, Basic, Pascal, C, C++, Java, Python, and C#.
• Compiler: translates a program written in a high-level language into machine language
• The equation, wages = rate × hours, can be written in C++ as:

  rate = 20;
  hours = 40;
  wages = rate * hours;

Introducing C++

• Without software, the computer is useless.
• Software is developed with programming languages like C++.
• C++ is suited for a wide variety of programming tasks with a focus on:
  • Performance
  • Efficiency
  • Flexibility of use

How does a C++ program run?

Processing a C++ Program

C++ Example Program

/*
 * Displays the message: "Hello World!"
 */
#include <iostream>
using namespace std;
int main()
{
    cout << "Hello World!" << endl;
    return 0;
}

Program Output when Run

Hello World!

The steps to process a C++ program

1. Create a plain-text file with the source program in C++
2. Preprocessor directives begin with # and are processed by the preprocessor.
3. Use the compiler to:
   • Check that the program obeys the language rules.
   • Translate into machine language (object program).
4. Linker:
   • Combines object program with other programs provided by a Software Development Kit (SDK) to create executable code.
   • Library: contains prewritten code you can use
5. Loader: Loads executable program into main memory.
6. The last step is to execute the program.

• Some IDEs (like Visual Studio) compile, link, and run with single Build or Rebuild command.
• IDE = Integrated development environment

An Early History of Computing

This is a great overview of the early computing, which is included in Chapter 1. You may skip to 2 minutes 27 seconds into the video to start.