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Summary Computing notes for GCSE AQA
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Computing notes for GCSE AQA
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1Explain the terms hardware and software ● Hardware are the physical aspects of a computer
system that can be touched
● Software are programs, written to run on a
computer system, includes programs that can
control and use the hardware.
● Hardware is the physical components of a system
whereas software is code that runs on the
hardware
Types of software ● Application software
○ Application software enables the user to
carry out productive tasks
○ E.g web browser, word processor, video
editing, spreadsheet
● System software
○ Set of computer programs that are
designed to manage the computer
system
○ Includes the OS and utility software
○ The OS is essential for the hardware to
run and for the user to interact with the
system
Operating systems ● Operating system is the software that is used to
manage the hardware within a computer system
● Examples include e.g microsoft windows, Mac OS,
android
● Operating system is a link between the hardware
and the software
● Functions of an operating system include:
○ Managing the human-computer
interface
○ Moving data to and from secondary
storage and file management
○ Sharing memory between software
○ Scheduling the processor and
multitasking of software
Utility programs ● Utilities are software tools that complement the
operating system in managing the smooth running
of the computer system
○ Encryption
■ Software scrambles a file so
that if it is accessed by an
unauthorised user it can't be
understood
○ Anti-spam
■ Software attempts to reduce
the amount of unwanted
emails received by an email
client
○ Backup
■ Utilities make automatic
backups of files and disks
○ Defragmentation
■ Utilities reorganise the data
stored on a disk so that large
data files and program files
are kept together rather than
spread out across a data
■ Speeds up data access
speeds
○ File compression
■ Utilities make files smaller in
size so that more can be fitted
onto a storage medium or to
make data transmission
● Describe two different functions performed by an
, operating system.
○ Memory management
■ Manages the computer's
memory
■ Schedules which processes
are to be executed
○ Processor management
■ Manage the computer's
processors (CPU)
■ Schedules which processes
are to be executed
○ Managing storage
■ Manage secondary storage
devices
■ Loading data and programs
into the computer's memory
■ Storage space management
Explain the ‘Von Neumann architecture’ ● Identified that data and programs could be stored
in the same memory
● Means only one set of RAM is required for storing
both data and programs
● Don't need two separate sets of memory
Explain the role and operation of main memory and the ● ALU
following major components of a central processing unit ○ Carries out arithmetic ( +, -, *,/)
(CPU): ○ Logical operations (AND, OR, NOT)
● CU
• arithmetic logic unit
○ Manages the execution of instructions
• control unit ○ Makes sure that all the components
• clock perform their tasks at the correct time
○ FDE Cycle
• bus ● Clock
○ Signal that synchronises tasks
○ Clock cycle
○ Each tick of clock CPU processes one
or more instructions
○ More clock speed more faster
instructions processed
● Bus
○ The CPU includes system bus
○ Set of wires connecting (CPU,Memory,
I/O)
○ Data bus (instructions and data items)
○ Control bus (control signals)
○ Address (memory addresses)
Explain the effect of the following on the performance of
the CPU:
• clock speed
• number of processor cores
• cache size
• cache type
, ● Clock speed
○ Number of clock cycles per second
○ More times a second the clock ticks,
more instructions carried per second
○ Overclocking (cause overheat and some
processes not being completed before
next instruction is started)
● Number of processor cores
○ A core is the processing unit which
receives instructions and performs
calculations
○ (Parallel processing) Allows different
instructions from the same program to
be run at the same time
○ (Multitasking) Allows instructions from
more than one program to run at the
same time
● Cache size
○ Cache memory is super fast memory
that is built into the CPU (recently used
instructions are stored in cache so they
can be used again quickly without
having to fetch them from main memory
(RAM))
○ If a processor has a large cache then it
can store more of the frequently used
instructions/data that can be accessed
by the processor
○ Improves performance because it is
more likely the instructions will be
retrieved from cache and not the slower
main memory
● Cache type
○ L1 - Part of the CPU,Fastest to access,
smallest size
○ L2 - Built into CPU, slower, larger
memory
○ L3 - larger but slower, not part of the
processor.
○ The closer the cache is to the CPU, the
faster the CPU can access the
instruction
Understand and explain the ‘Fetch-Execute cycle’ ● Fetch
○ The next instruction is fetched to
the CPU; from main memory;
● Decode
○ What the instruction is // what operation
is to be carried out is identified;
● Execute
○ The instruction is carried out; data may
be read from/written to main memory;
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