COMPUTER MEMORY UNIT
Subject:
COMPUTER SCIENCE
Term:
FIRST TERM
Week:
WEEK 3
Class:
SS 2
Topic:
MEMORY UNIT
Description of Memory Unit
Types of Memory
Description of Primary Memory
Description of Secondary Memory
Previous lesson:
The pupils have previous knowledge of
that was taught as a topic in the previous lesson
Behavioural objectives:
At the end of the lesson, the learners will be able to
- Define the meaning of memory unit
- Say the Description of Memory Unit
- Mention Types of Memory
- Give a vivid Description of Primary Memory
- Explain in details the Description of Secondary Memory
Instructional Materials:
- Wall charts
- Pictures
- Related Online Video
- Flash Cards
[mediator_tech]
Methods of Teaching:
- Class Discussion
- Group Discussion
- Asking Questions
- Explanation
- Role Modelling
- Role Delegation
Reference Materials:
- Scheme of Work
- Online Information
- Textbooks
- Workbooks
- 9 Year Basic Education Curriculum
- Workbooks
WEEK 3
CLASS: SS 2
SUBJECT: COMPUTER SCIENCE
TOPIC: MEMORY UNIT
CONTENT:
Description of Memory Unit
Types of Memory
Description of Primary Memory
Description of Secondary Memory
Sub-Topic 1: DESCRIPTION OF MEMORY UNIT
Computer memory is the storage location where data, programs and information are stored electronically, which can be recalled, erased or changed. Memory can also be defined as the work area in the computer where data can be held, copied and retrieved.
Other terms used for memory are main memory, main storage, primary storage, internal memory, and core storage.
There are two main types of memory, these are;
- Primary Storage/ main memory
- Secondary Storage / Auxiliary memory
PRIMARY MEMORY
Primary storage is called ‘primary’ because it is the main memory that is accessible to the CPU. It represents the core or internal storage areas of the computer system. It is used to store data that is currently being used; for this reason, the main memory is also called Immediate Access Storage (IAS).
The two types of primary storage are:
- Read Only Memory (ROM)
- Random Access Memory (RAM)
READ ONLY MEMORY (ROM)
ROM is a non-volatile memory chip that cannot be written on or erased by the computer user without special equipment. The ROM retains data stored on it even after the computer is powered off. The operating system boot records are stored inside the ROM.
There are different variations of ROM, these includes;
- PROM: Meaning Programmable ROM is a version of memory chip that can be programmed by the user. Once the PROM has been programmed, the information is permanent and cannot be erased or deleted.
- EPROM: means Erasable Programmable This version of memory chip can be erased and reprogrammed with the aid of an Ultraviolet light.
- EEPROM: means Electrically Erasable Programmable ROM can be erased and reprogrammed using an electrical charge without the need of removing the chip from the computer system.
RANDOM ACCESS MEMORY
Random Access memory (RAM) is a type of memory chip used in primary storage memory. The CPU continuously reads instructions stored there and executes them as required. Any data actively operated on is also stored there in a uniform manner. It is also temporary storage, holding software instructions and short-term working memory for the processor. It allows data which is stored to be
accessed in any order, which is why it is called random. It determines the speed of processing of the computer. Also, RAM is volatile; which means when the computer loses power, the content is lost.
There are two variations of RAM, these are;
- SRAM: Means Static Read Only Memory; In this type of memory the data is stored in cell of transistors and capacitors and the data has to be refreshed every few milliseconds.
- DRAM: Means Dynamic Read Only Memory; This does not require periodical refresh. SRAM is faster than DRAM but it is more expensive as compared to DRAM.
EVALUATION
- Define and give two other names for memory unit
- List the two main types of memory
Sub- Topic 2: SECONDARY MEMORY
Secondary storage or auxiliary storage is any storage device that is used to store data, information and programs permanently outside the computer memory. They are non-volatile and have higher storage capacity, but the access time is slow compared to the primary storage. It is also referred to as backup storage.
The following are common types of secondary / auxiliary devices:
- Floppy Disk
- Hard Disk
- Flash Drive
- Compact Disk (CD)
- Digital Versatile Disk (DVD)
FLOPPY DISK
Floppy disk is a soft magnetic disk. It is called floppy because it flops if you wave it. Floppy disks, also called diskettes, are portable because you can remove them from a disk drive. The medium used to access floppy disks is known as ‘Floppy Disk Drives’.
Floppy disks are slower to access than hard disks and have less storage capacity. Floppies come in three basic sizes; 8-inch, 5.25 inches with a capacity of 1.2MB and 3.5 inch with a capacity of 1.44MB.
HARD DISK
This is a magnetic disk on which computer data can be stored. The term hard is used to distinguish it from soft, or floppy disk. It has the capability to store more data and is faster than floppy disks in terms of access time.
There are two types of hard disks:
- The internal hard disk installed inside the computer
- The external hard disk is usually connected to the computer
FLASH DRIVE
A Flash drive is a high data storage device that is made up of flash memory and an integrated Universal Serial Bus (USB) interface, with a storage capacity ranging from 64MB to over 8GB. The device is connected to the computer through the USB port.
COMPACT DISK
The Compact Disc (CD) is an optical disk used to store and backup digital data. It is less vulnerable to damage or dirt compared to floppy disk. They are generally of two types:
- CD-R meaning CD Data on this type of disk can be written only once, after that the data on disk becomes permanent, i.e it can neither be erased and no newer data be written on this disk.
- CD-RW meaning CD You can record the
DIGITAL VERSATILE DISK (DVD)
A Digital Versatile Disk – originally called digital video disk is an optical disk storage media format, invented and developed in 1995. DVDs offer higher storage capacity than compact disks while having the same dimensions. Also, they can be single sided or double sided.
EVALUATION
- What do you understand by ‘Secondary Memory’
- Highlight five types of auxiliaries
GENERAL EVALUATION
- Mention two main types of Primary storage
- Highlight the different types of ROM
- Highlight the different types of RAM
- Enumerate three characteristics of secondary memory
READING ASSIGNMENT
Study the topic ‘UNITS OF COMPUTER STORAGE’ using your students’ textbook
WEEKEND ASSIGNMENT
- Which of this best describes ROM? (a) non-programmable memory (b) Non-volatile memory (c) user-programmable memory(d) microscopic-sized memory chip
- These are auxiliary memory except(a) cache (b) floppy disk (c) flash drive (d) digital versatile disc
- The information: ‘Memory (RAM): 0GB’ refers to(a) speed of processing unit (b) number of registers (c) size of primary memory (d) serial number of random-access memory chip
- The ROM stores data and instruction during program execution (True / False)
- Another name for the primary / main memory ……………………………
ESSAY QUESTIONS
- State three differences between primary and secondary memory
- State the three basic sizes of a floppy disk
[HDquiz quiz = “821”]
