1. A451: Computer Systems and Programming

2. 2.1.2 Memory

3. What is your earliest memory??

4. Learning Outcomes Wednesday, 27 February 2019
describe the difference between RAM and ROM (h) explain the need for ROM in a computer system (i) describe the purpose of RAM in a computer system (j) explain how the amount of RAM in a personal computer affects the performance of the     computer (k) explain the need for virtual memory (l) describe cache memory (m) describe flash memory (n) discuss how changes in memory technologies are leading to innovative computer designs.
Wednesday, 27 February 2019

5. Memory ROM and RAM
Memory is used to store program instructions and data as a string of zeros and ones. There are two main types of computer memory, RAM and ROM
ROM stands for Read only Memory, this means that the contents of ROM can only be read. It cannot be deleted or edited.
An example of ROM is the BIOS (Basic Input Output System), This chip is supplied by the manufactures of the computer and contains all the instructions to boot up the computer when you turn the power on.
The instruction are permanently saved onto the ROM and are always present even when the power is turned off. This memory is referred to as non –volatile memory

6. RAM
RAM standards for Random Access Memory. It stores all the current instructions that the software being used requires and temporally stores data being processed by the CPU.
If you consider looking for a friend who lives in a block of flats, you could access any floor randomly. RAM works the same, the computer can access any memory location at Random and either read or write data to that memory address.
Memory addresses are like buckets filled with water. If the bucket is full then it represents the value 1, if empty, the value 0. Obviously RAM does not use water but electrical charge. If the address has a charge then it represents a value of 1, this can be used to build up a sequence of zeros and ones, a binary code which can be converted into a set of instructions.

7. RAM
Since the data in RAM is stored as an electrical charge if the power supply is cut or stopped then then all the contents of the RAM are wiped. RAM is often referred to as Temporary or Volatile storage.
When loading and using software the program instructions are loaded into RAM. As more software is loaded his takes up more Memory in RAM. Eventually the memory space runs out and RAM has to overwrite previous Memory addresses. This has the impact of slowing down the overall computer performance as the data has to be re written and relocated if the instructions are required.

8. Example
WORD
MP3
BROWSER
PHOTO
Software is not completely uploaded, some instructions are not stored into the RAM
Software being loaded into the ram, eventually I becomes full and connect load all the photo software, so some is missed out, if it is required then the ‘word’ program has to be removed from RAM to make room for the rest of the ‘Photo’ program.

9. COMPARISON RAM ROM Random Access Memory Volatile
Stores a electronic charge to represent a value of ‘1’
Memory location can be deleted and written to
Used for storing data or program instructions that are currently being used
Increasing amount of RAM will increase the computers overall speed
Read Only Memory
Non Volatile
Usually uses Flash memory
Contents cannot be deleted
BIOS is a common ROM chip

10. Virtual Memory
Virtual Memory is a location on the Hard Disk which is used as a storage for program or software instructions that will not fit into RAM.
If the RAM is full then some of the content can be temporally written to the hard disk and retrieved when required. This saves the computer from slowing down.
CPU
RAM
VIRTUAL MEMORY

11. Cache Memory
Most computer and laptops have several cache stores. An instruction cache can be used to store the most common used instructions and this speeds up the fetch, decode, execute cycle as the data is does not require fetching and is already decoded. A data Cache can speed up reading and writing users or program data to and from memory locations.
RAM
DATA
Common used data
CPU
Common used instructions
INSTRUCTIONS

12. Flash Memory
Flash memory is a commonly used non-volatile computer storage memory, it is electrically erased and rewritten. Flash memory is official called EEPROM electrically erasable programmable read-only memory Most Flash memory is used in SD cards, USB flash drives, solid-state drives, and used in laptops, mobile phones digital cameras and games consoles The technology flashes’ the memory components within the device to remove the charge from electrons. If there is no charge then this is interpreted as a zero value. A value of one is assigned if electronically charge is present. Flash memory is very easy to manufacture and large amounts od data can be written to relatively small spaces. .

13. True OR False CPU stands for Central Processing Unit
RAM has an impact on overall computer speed
The ALU performs calculates and arithmetic.
Clock speed is a measure of memory
The program counter keeps track of which program instruction is currently being executed
The Central Unit controls the memory
Decode, Fetch, execute
The IAS performs logic calculation
CPU speed is measured in Hertz
RAM can only access memory addresses in numerical order
Processors can only have one core
the BIOS is violate memory

14. What have you learnt today?
Plenary
“Share with your table one new thing you have learnt today” Log onto Socrative and complete the Learning questions
What have you learnt today?