Boost your exam performance with our top-notch Computer Science Revision Notes, meticulously compiled from official mark schemes of past papers. These concise, exam-focused notes cover all topics in 1.2 (Types of software and the different methodologies used to develop software) of the A Level OCR ...
1.2 - Types of software and
the different methodologies
used to develop software
,Operating system
Operating Systems (OS): Software that manages the hardware and
software resources of a computer system.
Their purpose is to enable the user to communicate with the computer
and perform certain tasks.
The OS has many functions such as:
● Memory Management
● Provide a user interface
● Provide utilities for system maintenance
● Provide security
,Memory Management
When data & programs are being used, its retrieved from secondary
storage and placed into memory.
Memory management needs to ensure that RAM is used efficiently so
that space is not wasted and data is secure. It does this in many ways:
● Removal of unnecessary data to free up space
● Allocation of memory to applications
● Splitting up of memory
, Paging & Segmentation
Storing programs as a single block of memory is wasteful because parts
of the program not being used are taking up space.
Paging: The splitting up of memory into physical divisions, known as
pages, which are equal in size.
- It's easier for OS to manage pages as they are stored non-contiguously
- Paging causes internal fragmentation
Segmentation: The splitting up of memory into logical divisions, known
as segments, which vary in size according to its contents.
- Segments work better contiguously
- Segmentation causes external fragmentation
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