Post date: Nov 15, 2014 10:02:42 PM
Logic Operations
NOT operations
a
0
1
NOT a
1
0
AND operations
OR operations
XOR operations
World Wide Web (WWW or Web)
The Web today is a repository of information in which the documents, called Web pages. And the linking of web pages was achieved using a concept called hypertext, which used a machine that automatically retrieved another document stored in the system when a link to it appeared in the document. Today, the Internet has been changed to hypermedia to show that a web page can be a text document, an image, au audio file or a video file.
HyperText Transfer Protocol (HTTP)
A protocol that is used to define how the client-server programs can be written to retrieve web pages from the web. An HTTP client sends a request, an HTTP server returns a response.
Range of mid-semester exam
Chapter 1-3, Chapter 4 (page 76-81), Chapter 5 (page 100-105), Chapter 6 (152-155)
Assignment (definitions)
Central Processing Unit (CPU)
It performs operation on data. It contains three parts: Arithmetic Logic Unit (ALU), Control Unit, and a set of registers, fast storage locations.
Arithmetic Logic Unit (ALU)
It performs logic, shift and arithmetic operations on data.
Logic operations
It contains several logic operations, NOT, AND, OR and XOR.
Shift operations
It used to shift bit patterns to the left or right, while arithmetic operations are applied to integers.
Arithmetic operations
Some operations can be implemented more efficiently in hardware.
Registers
They are fast stand-alone storage locations that hold data temporarily. They including: Data registers, Instruction registers and Program counter.
Data registers
Their responsibilities are holding the intermediate results temporarily to speed up the computers since complex operations are done using hardware instead of software. These are named R1 to Rn.
Instruction registers
The CPU is responsible for fetching instructions one by one from memory, storing in the instruction registers, decoding and executing them.
Program Counter
It keeps track of the instructions currently being executed. After executing instructions, it is incremented to point to the address of the next instruction in memory.
Control Unit
It controls the operation of each subsystems.
Main Memory
It is the second major subsystem in computer. It exists two main types, RAM and ROM.
Random Access Memory (RAM)
The CPU can write something to RAM and later overwrite it. It also volatile, that is meant the information (program or data) is lost if computer is powered down. RAM also divided into two, SRAM and DRAM.
Static Random Access Memory (SRAM)
It uses traditional flip-flop gates to hold data. The gates hold their state (0 or 1), which means that data is stored as long as the power on and there is no need to refresh memory locations. Hence, it is fast but expensive.
Dynamic Random Access Memory (DRAM)
It uses capacitors, electrical devices that can store energy for data storage. If a capacitor is charged, the state is 1, instead, the state is 0. Since a capacitor loses some of its charge with time, it need to be refreshed periodically, hence, it is slow but inexpensive.
Read-Only Memory (ROM)
It written by manufacturer, and the CPU can read it but cannot overwrite it. Hence, it is nonvolatile.
Programmable Read-Only Memory (PROM)
User might store program on it within some special equipment.
Erasable Programmable Read-Only Memory (EPROM)
It can be programmed by user, can also be erased with a special device that applied UltraViolet (UV) light. To erase EPROM requires physical removal and reinstall.
Electrically Erasable Programmable Read-Only Memory (EEPROM)
It can be programmed and erased using electronic impulses without being removed from the computer.
Cache memory
It is faster than main memory but slower than CPU and its registers. The procedure in order is CPU will checks the cache. If the words are there, it copies the words, instead, CPU accesses main memory and copies a block of memory starting with the desired words. This block will replaces the previous contents in cache memory. So that, CPU accesses the cache and copies the words.