【Lecture1】Computer Systems & Networks
Contents
- 1. CPU
- 2. Five Generations of Computers
- 3. Moore’s Law – 1965
- 4. History of Computing
- 5. Data Representation
CPU
Transistor
Transistors are the building blocks of integrated circuits, such as computer processors, or CPUs. Modern CPUs contain millions of individual transistors that are microscopic in size.
Vacuum Tubes
Though the precursors of the transistor were invented in 1907 (at the time they were not transistors yet, they were vacuum tubes, also called as valves), these were soon replaced by smaller components called transistors. These are still the key components of modern computers nowadays.
What is a transistor?
- Base
- Collector
- Emitter
A transistor is an electronic component with three pins. Basically, a transistor is a switch (between two of the pins: the collector and the emitter) that is operated by having a small current in the third pin called the base.
When a small current is applied to the base, it means “on” which collector can send the voltage to the emitter. Also when a small current is not applied to the base, it means “off” which collector can’t send the voltage to the emitter.
This is why the transistor is called a switch which they can do “on” and “off”.
» More details (Japanese Article)
Transistors come in many shapes and sizes. ALso, transistors are made by layering three types of materials: conductors, insulators and semiconductors.
» Recommended Youtube About Transistor
Logic Gates
Explanation 1
Logic Gates are made by combining transistors. They enable us to apply logic to small currents which are either turned on or off and represent binary information inside a computer. Computers are made by combining logic gates together.
Explanation 2
Logic gates allow our transistors to do more complex tasks, like decide where to send electrical signals depending on logical conditions.
For the “And Gate”, both of the transistors have to be “on” to output “1”, which is possible to make this logic happen by using 2 transistors directly because if one of them’s base didn’t have the current, the voltage cannot be sent through.
Integrated Circuits
An integrated circuit (also referred to as a chip, or a microchip) is a set of electronic circuits on one small flat piece (or “chip”) of semiconductor material, normally silicon. The integration of large numbers of tiny transistors into a small chip results in circuits that are smaller, cheaper, and faster than those constructed of discrete electronic components.
Mirco-Processors
A microprocessor is a computer processor which incorporates the functions of a computer’s central processing unit (CPU) on a single integrated circuit (or at most a few integrated circuits). The microprocessor is a multipurpose, clock driven, register based, digital-integrated circuit which accepts binary data as input, processes it according to instructions stored in its memory, and provides results as output.
» More details (Japanese Article)
Digital Circuit
A digital circuit is designed by using a number of logic gates on a single integrated circuit – IC. The input to any digital circuit is in the binary form “0’s” and “1’s”. The output obtained on processing raw digital data is of a precise value. These circuits can be represented in 2 ways either in a combinational way or a sequential way.
» More details (Japanese Article)
Five Generations of Computers
- 1st Generation Computers: Vacuum Tubes
- 2nd Generation Computers: Transistors
- 3rd Generation Computers: Integrated Circuits
- 4th Generation Computers: Micro-Processors
- 5th Generation Computers: Nowadays
1st Generation Computers: Vacuum Tubes
Back in the 1950s, computers consisted of vacuum tubes called valves (the precursors of transistors). These valves were quite bulky, like electric bulbs, and produced a lot of heat. The installations used to fuse frequently.
Punch cards, paper tape, and magnetic tape were used as input and output devices. 1st Generation Computers were programmed using machine code.
1st Generation Computers were very expensive and only large organisations were able to afford them.
2nd Generation Computers: Transistors
In the early 1960s, 2nd Generation computers used transistors to replace the vacuum tubes of 1st generation computers. Therefore 2nd Generation computers were cheaper, consumed less power and were more compact in size. They were also more reliable and faster. More transistors could be used to create more complex computers.
Magnetic tape and magnetic disks were used as secondary storage devices as well as punched tapes which were still used.
2nd Generation Computers were programmed using assembly language and high-level programming languages such as FORTRAN or COBOL.
3rd Generation Computers: Integrated Circuits
In the second half of the 1960s, integrated circuits were used by 3rd Generation Computers. An integrated circuit has many transistors, resistors, and capacitors along with the associated circuitry. This development made computers smaller in size, more reliable and efficient.
3rd Generation Computers were programmed using High-level languages (FORTRAN, COBOL, PASCAL, BASIC, ALGOL-68 etc.).
4th Generation Computers: Micro-Processors
In the 1970s, Computers of 4th generation used Very Large Scale Integrated (VLSI) circuits. VLSI circuits having about 5,000 transistors on a single chip called a micro-processor.
Fourth generation computers became more powerful, compact, reliable, and affordable. They started the Personal Computer (PC) revolution.
5th Generation Computers: Nowadays
The period of fifth generation is 1980-to date. In the fifth generation, VLSI technology became ULSI (Ultra Large Scale Integration) technology, resulting in the production of microprocessor chips having ten million electronic components.
Moore’s Law – 1965
The rate at which transistor counts have increased generally follows Moore’s law, which observed that the transistor count doubles approximately every two years. As of 2016, the largest transistor count in a commercially available single-chip processor was over 7.2 billion.
But it’s not relevant today anymore because it’s physically impossible to create anymore (It got too small).
History of Computing
1. Mechanical Computers – 1840
- Charles Babbage’s Difference Engine
- For calculating tables eg (sine & polynomial)
- Used gears and wheels and other mechanical movements
- You had to turn a crank handle to make it work
2. Electromechanical Computers – 1940
- First built from relays and were slow & noisy
- ENIAC: first fully electrical computer using vacuum tubes
- Designed for calculating bombing trajectories
- It was huge, and Less powerful than a pocket calculator
3. Electronic Computers – 1950s
- First electronic computers used up to 20,000 vacuum tubes instead of relays.
- Vacuum tubes generated a lot of heat and consumed as much power as a small city
- With the invention of the transistor in the early 1950’s computers were finally set to take off
First Integrated CPU – 1971
- Intel 4004 Processor
- 4bit Data + 8bit instruction
- Contained 2300 transistors
- Clock speed 100kHz
- Addressable memory was 640 Bytes
- Used to build worlds first pocket calculator
Data Representation
| Name | Base | Digits You Count |
| Decimal | Base 10 | 0,1,2,3,4,5,6,7,8,9 |
| Binary | Base 2 | 0,1 |
| Octal | Base 8 | 0,1,2,3,4,5,6,7 |
| Hexadecimal | Base 16 | 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F |
From Decimal to Binary
From Binary to Decimal (There’s 2 ways)
From Binary to Octal
From Octal to Binary
From Binary to Hexadecimal
From Hexadecimal to Binary
Others
For others, such as from Hexadecimal to Octal, you have to convert from Hexadecimal to Binary at first. Then, you can convert from Binary to Octal. So basically when you convert from sth to sth, there should be Binary in one of them.