Ict notes
A computer system is a set of equipment that works together to help you do useful work
𝐼𝑛𝑝𝑢𝑡 → 𝑝𝑟𝑜𝑐𝑒𝑠𝑠𝑜𝑟 → 𝑜𝑢𝑡𝑝𝑢𝑡 → 𝑠𝑡𝑜𝑟𝑎𝑔𝑒
The processor
At the Centre of a computer, system is a processor. The processor does all the work in a computer system
a processor is small enough to fit on your fingertip modern processor are so tiny they called
microprocessors
Part of the CPU
The control unit (cu) manages the work done by cpu when an instruction arrives at the cpu it goes to the
cu the cu works out what instruction means the cu makes sure that the other parts cpu do the work
necessary to carry out the instructions .
The arithmetic and logic unit (alu) does all the calculations in the CPU. The cu sends the instructions to
the alu and it carries out the instructions this is similar to using a spreadsheet to do your calculations.
The clocks sends out regular electric pulses just like the tick of a clock. A clock at home tick every second.
The clock in a computer CPU ticks around 3billions times every second every time the cpu clock ticks the
control units sends an instruction to the alu
Buses
Connected called buses join the three parts of a CPU together. Buses are high speed connected that carry
data around inside the CPU
How the CPU works
Think about the last time you played a game or watched a video on a computer. The screen is fully of color
the image are life like and objects more just like they do in the real world if you are playing a video
game you can give instructions through a joystick or a game controller
The fetch execute cycle
Memory and the cpu
The cpu is the part of the computer that carries out the instructions it is made up of control unit the alu
and a clock all connected by buses the computer memory is very close to the cpu it is joined the cpu
the computer memory is sometimes called the memory unit is sometimes called IAS (immediate access
store ) RAM(random access memory)
What is in memory
The memory hold:
The instructions that tells the computer what do
The data values the computer need
How does the memory work
Memory is made up of microscopic electrical circuits the circuit can be across everything inside the
memory is stored using on loss signals the on loss signals can be shown as 1 and 0 in binary
Memory and storage
Data is stored in memory as electrical signals all data is lost if the electrically
Complex logical statement
Increasing complexity
In this lesson, we will learn how to describe situations where there are more parts to the logical argument
Here is an example
A football club wants to sign a new star player the manager has asked the team owner to sign a player
who scored 30goals last season the manger also wants the player to be left footed here are the key points
clubs signs player players is left footed
Using and to link logical statement
1. Write out the argument
The first to identify the conclusions there only ever one conclusion to a logical statement the
conclusion is the ‘club signs player’.
Once the conclusion is identified any other statement are part of the propositions ‘player is leftfooted ‘players scored 30goals are the propositions
The two statements must be joined together the statements can be joined using AND or OR if
both statements must be true join them with AND
2. Create the column headings in this example the table must have three columns the conclusion
must always go in the column on the far right
Players is left footed
Players scored 30 goals
Clubs signs players
3. Add a row for every possible response to the proposition
Players is left footed
Played scored 30goals
False
False
False
True
True
False
True
True
Clubs signs players
4. Complete the conclusion column the two parts of the proposition are joined by AND . this
means that the conclusion will be true only if both parts of the propositions are true
Players is left footed
Players scored 30goals
Clubs sign players
False
False
False
False
True
False
True
False
False
True
True
True
The final tables tell us that clubs sign player is true only when both players is left footed and
players scored 30goals are true
Logic gates
A computer can carry out complicated tasks such as creating realistic games it can navigate a spacecraft
through space how this is possible when a computer is only made up of switches that can be turned on or
off.
Type of logic gates



The AND gate
The or gate
The not gate
The CPU is made up of millions of on off switches these switches are organized into larger units called
gates one of these gates is the (and gates) each type of gates that a computer uses has its own symbols
the and gate has two inputs they are called a and b the gate is inside the cpu so it can only understand
binary the output of and gate is 1 if both input a and b are 1 otherwise it is 0 you can draw a truth table
for the and gate
A
0
0
1
1
B
0
1
0
1
OUTPUT
0
0
0
1
The or gate
Another type of gate the computer uses is an or gate. The or gate has two inputs they are labeled input a
and b it has one output. The value of each input can be either input a or input b or both is 1
The truth table
A
1
0
1
0
B
O
1
1
0
OUTPUT
1
1
1
0
The not gate
Other gates are used in a computer they help us get the answers we need a not gate has only one input
and one input a not gate reverses the input if the input is 1 the output is 0 and vice versa
Input
Output
0
1
1
0
Circuits
Gates become more powerful and more useful when they are joined together
When gates are joined together they form a circuit
A
0
0
1
1
B
0
1
0
1
C
0
0
0
1
Z
1
1
1
0