1. BACS 287
Basics of Programming
BACS 287

2. History of Computers
Early “computers” mechanized the calculation process
Charles Babbage designed the analytical engine - first with stored memory in early 1800s
Herman Hollerith built a punched card tabulating machine in 1880s
None of these were “true” computers
Abacus - earliest computing devices - ancient Egypt and China
1st mechanical adding machine - add and subtract Blaise
Pascal
1st mechanical calculating machine - multiple and divide too -
Gottfried Liebnitz 1692
Charles Babbage - professor of mathematics at Cambridge
- Difference engine - perform calculations and print
results without human intervention
- Analytical Engine - designed but not built - had memory
unit, arithmetic unit, punched card input
Herman Hollerith - tabulating machine - process US census in 1890
1896 the Tabulating Machine Company that later merged with 12 other companies to form IBM
None of these were true computers because they did not have a way to internally store its own program and memory.
BACS 287

3. History of Computers First true computers developed during W.W.II
EGNIMA - early 1940s
Colossus - early 1940s
MARK I
ENIAC
EDVAC, EDSAC
UNIVAC I
EGNIMA was German code machine, not true computer
Colossus was British counter machine to break German code
MARK I was essentially Babbage difference engine. Had program entry via punched paper tape.
ENIAC (Electronic Numerical Integrator and Calculator) 1st US computer. Did not use stored program - used wire board.
EDVAC (U.S.) , EDSAC (Electronic Delay Storage Automatic Computer) - (England) had internally stored programs
UNIVAC I - First commercial system. Delivered to census in First business use was GE in 1954
IBM first commercial computer for IBM
IBM dominance did not take off until 1960 with IBM 1401 followed by the IBM 360.
UNIVAC I and IBM 650 were 1st generation hardware
BACS 287

4. Hardware/Software Generations
1st Generation Hardware
Vacuum tubes
Punched cards, Paper tape
Magnetic tape available
Machine language
Millisecond access time
1st Generation Software
Machine language
Specific to CPU
tedious, error prone
time consuming
1-to-1 instruction ratio
explicit control
fast execution (within hardware limitations)
BACS 287

5. Hardware/Software Generations
2nd Generation Hardware
Discrete Transistors
Punched Cards, paper tape
Magnetic tape
Assembly language
Microsecond access time
2nd Generation Software
Assembly language
mnemonics
symbolic names
relocatable code
explicit control
usually 1-to-1 instruction ratio
fast (within hardware limitations)
BACS 287

6. Hardware/Software Generations
3rd Generation Hardware
Integrated circuits
Magnetic Disk
High-level languages (COBOL,Fortran...)
> 100 Nanosecond access time
3rd Generation Software
High-level languages
portable between machines
instruction explosion
relatively English-like
problem specific
less control
less speed than low level languages
BACS 287

7. Hardware/Software Generations
4th Generation Hardware (...)
large scale Integrated circuits
Mass Storage devices
4th Generation languages (Easytrieve, Mapper)
1-10 Nanosecond access time
4th Generation Software (...)
4th generation
less procedural, more problem oriented
graphically oriented
built-in code generation facilities
less control
less speed than low level
BACS 287

8. Hardware
Hardware are the physical devices that make up a computer system
Hardware systems are “tuned” to work together
There are five basic hardware components in a computer system
BACS 287

9. Hardware Components of a Computer System
Input & Output Devices
Central Processing Unit (CPU)
Primary Storage (RAM)
Secondary Storage (disk)
Communication Devices
BACS 287

10. CPU The “brains” of the computer
Executes instructions to perform simple functions
Capable of executing only one instruction at a time
Executes instructions in billionths of a second (i.e., nanoseconds)
Composed of several sub-components
BACS 287

11. CPU Sub-Components Control Unit (CU) Arithmetic and Logic Unit (ALU)
Registers
Cache memory
Clock
and others...
BACS 287

12. Primary Storage Random Access Memory (RAM) Volatile storage
All computer programs must be in RAM before the CPU can execute them
Access time normally measured in nanoseconds (billionth of a second)
Relatively limited amount of RAM in a system
BACS 287

13. Secondary Storage Hard disks, floppy disks, tape, ...
Non-Volatile storage
Large Capacity -- Relatively Slow
Most rely on moving parts
Access time normally measured in thousandths of a second (milliseconds)
Speed difference between RAM and Disk is tremendous
BACS 287

14. Software Software is the logical component of a computer system
Software are detailed instructions (procedural logic) that tell the CPU how to solve a problem
There are various levels (types) of software; each has a specific purpose
The three types are 1) operating systems, 2) compilers and interpreters, and 3) application programs
BACS 287

15. Operating System A program that works directly with the hardware
Provides useful services that application programs need
Usually written in low level languages (e.g., assembler, C) to work on a specific CPU
“Windows” is an operating system
BACS 287

16. Compilers and Interpreters
Utilities to translate English-like source code into executable object code for the CPU
Compilers translate the entire program as a unit and save the results
Interpreters translate one line at a time and discard the results after execution
Visual Basic can be both an interpreter and a compiler.
BACS 287

17. Application Programs
Application programs are software that perform end-user tasks
Normally, high-level and very specific (e.g., spreadsheet, word processor)
You can write applications programs using Visual Basic and other computer languages
BACS 287

18. Where this class fits into the picture
In this class you use a compiler (& interpreter) running under the control of the operating system (on the hardware) to write application programs.
Generally speaking, it is incorrect to say that you are “programming” when you use an application program (like Excel or Access).
Programmers write new applications; they don’t utilize existing packages.
BACS 287

19. Quiz What is the difference between hardware and software?
What are the 5 components of a “true” computer?
What is the difference between a compiler and an interpreter?
What is the main difference between primary storage and secondary storage?
What is the main difference between 2nd generation and 3rd generation programming languages?
BACS 287