The Computer Architecture And Programming

Published Date: 02 Nov 2017

The computer system is divided into several units for its operation. These are as follows;

Input unit – This is the "receiving" section of the computer. It obtains information (data and computer programs) from input devices and places this information at the disposal of the other units for processing. Most information is entered into computers through keyboards and mouse devices. Information also can be entered in many other ways, including by speaking to your computer, scanning images, uploading digital photos and videos, and receiving information from a network, such as the Internet.

Output unit - This is the "shipping" section of the computer. It takes information that the computer has processed and places it on various output devices to make the information available for use outside the computer. Most information output from computers today is displayed on screens, printed on paper or used to control other devices. Computers also can output their information to networks, such as the Internet.

Memory unit - This is the rapid-access, relatively low-capacity "warehouse" section of the computer. It stores computer programs while they are being executed. It retains information that has been entered through the input unit, so that it will be immediately available for processing when needed. The memory unit also retains processed information until it can be placed on output devices by the output unit. Information in the memory unit is typically lost when the computer’s power is turned off. The memory unit is often called with memory or primary memory.

Please Note: Historically, this unit has been called "core memory," but that term is fading from use today.

Arithmetic and logic unit (ALU) – This is the "manufacturing" section of the computer. It is responsible for performing calculations, such as addition, subtraction, multiplication and division. It contains the decision mechanisms that allow the computer, for example, to compare two items from the memory unit to determine whether they are equal.

Central processing unit (CPU) - This is the computer’s "administrative" section. It coordinates and supervises the other sections’ operations. The CPU tells the input unit when information should be read into the memory unit, tell the ALU when information from the memory unit should be used in calculations and tells the output unit when to send information form the memory unit to certain output devices. Many of today’s computers have multiple CPUs and, hence, can perform many operations simultaneously—such computers are called multiprocessors.

Secondary storage unit - This is the computer’s long-term, high-capacity "warehousing" section. Programs or data not actively being used by the other units normally are placed on secondary storage devices, such as your hard drive, until they are needed, possibly hours, days, months or even years later. Information in secondary storage takes much longer to access than information in primary memory, but the cost per unit of secondary storage is much less than that of primary memory. Examples of secondary storage devices include CDs and DVDs, which can hold hundreds of millions and billions of characters, respectively.

Question 2

Differentiate the terms ROM, RAM and secondary storage.

Computer data storage, often called storage or memory, is a technology consisting of computer components and recording media used to retain digital data. There are two (2) types; primary storage, (RAM, ROM) and secondary storage.

Please Note: Primary memory itself is implemented by two types of memory technologies. The first is called Random Access Memory (RAM) and the other is read only memory (ROM). The other part of primary memory is implemented using ROM which stands for Read Only Memory.

Here are the top five differences between the two types of primary memory:

RAM is Random Access Memory.

ROM is Read Only Memory.

RAM is the memory available for the operating system, programs and processes to use when the computer is running.

ROM is the memory that comes with your computer that is pre-written to hold the instructions for booting-up the computer.

RAM requires a flow of electricity to retain data (e.g. the computer powered on).

ROM will retain data without the flow of electricity (e.g. when computer is powered off).

RAM is a type of volatile memory. Data in RAM is not permanently written. When you power off your computer the data stored in RAM is deleted.

ROM is a type of non- volatile memory. Data in ROM is permanently written and is not erased when you power off your computer.

There are different types of RAM, including DRAM (Dynamic Random Access Memory) and SRAM (Static Random Access Memory).

There are different types of ROM, including PROM (programmable read-only memory) that is manufactured as blank memory (e.g. a CD-ROM) and EPROM (erasable programmable read-only memory).

There are many differences between RAM and ROM memory but there are also a couple similarities (and these are very easy to remember). Both types of memory used by a computer, and they are both required for your computer to operate properly and efficiently.

Primary memory/storage vs. Secondary memory/storage

Processor access the primary memory in a random fashion. Unlike primary memory, secondary memory is not directly accessed through CPU. The accessing of the primary memory through CPU is done by making use of address and data buses, whereas input/ output channels are used to access the secondary memory.

The primary memory is embedded with two types of memory technologies; they are the RAM (Random Access Memory) and ROM (Read Only Memory). The secondary memory is accessible in the form of Mass storage devices such as hard disk, memory chips, Pen drive, floppy disk storage media, CD and DVD.

Primary memory is volatile in nature, while secondary memory is non-volatile. The information that is stored in the primary memory cannot be retained when the power is turned off. In case of secondary memory, the information can be retrieved even if the power is turned off because the data will not be destructed until and unless the user erases it.

When the data processing speed is compared between the primary and secondary memory, the primary memory is much faster than the secondary memory.

In the cost perspective, the primary memory is costlier than the secondary memory devices. Because of this reasons most of the computer users install smaller primary memory and larger secondary memory.

As the secondary memory is permanent, all the files and programs are stored in the secondary memory most and as the primary memory interacts very fast with the micro-processor, when the computer needs to access the files that are stored in the secondary memory, then such files are first loaded into the primary memory and then accessed by the computer.

Question 3

What is a hardware description language and what is its importance in the design of integrated circuits? List any three HDLs.

In electronics, a hardware description language or HDL is any language from a class of computer languages, specification languages, or modelling languages for formal description and design of electronic circuits, and most-commonly, digital logic. It can describe the circuit's operation, its design and organization, and tests to verify its operation by means of simulation.

Examples of HDLs;

HDLs for analog circuit design;

Name

Description

Analog Hardware Descriptive Language

an open analog hardware description language

SpectreHDL

a proprietary analog hardware description language

HDLs for digital circuit design;

The two most widely-used and well-supported HDL varieties used in industry are Verilog and VHDL.

Name

Description

Altera Hardware Description Language (AHDL)

a proprietary language from Altera

Question 4

What is an instruction set architecture (ISA)? Compare and contrast RISC and

CISC architectures.

The Instruction Set Architecture (ISA) is the part of the processor that is visible to the programmer or compiler writer. The ISA serves as the boundary between software and hardware.

RISC – Reduced instruction set computing, or RISC is a CPU design strategy based on the insight that simplified (as opposed to complex) instructions can provide higher performance if this simplicity enables much faster execution of each instruction. A computer based on this strategy is a reduced instruction set computer, also called RISC.

CISC – Complex Instruction Set Computers, In contrast to RISC, CISC chips have a large amount of different and complex instruction to make life easier for the programmer by reducing the amount of instructions required to program the CPU.

Advantages and Disadvantages

RISC

Produces faster and cheaper processors

Apple Mac G3 instructions are executed over 4x faster over its Intel equivalent.

Simpler hardware

Shorter design cycle

Requires more lines of code that becomes increasingly complex

Despite the speed advantages of the RISC processor, it cannot compete with a CISC CPU that boasts twice the number of clock cycles

Code debugging, code expansion and system design are the areas that become contentious subjects

CISC

Expensive processors than RISC types

Comparatively slow

Efficient coding means easier life for developers and the result has been some tremendous software that RISC users could not

AMD, Cyrix, and Intel have driven the market very well and outwit the RISC based technology, where Macs once were fighting with problems to 500MHz+ PowerPC chips, their contemporaries were looking 1GHz processors.

Microprogramming is as easy as assembly language to implement

CISC machines upwardly compatible

The compiler does not have to be as complicated

Instruction set & chip hardware become more complex with each generation of computers

Different instructions will take different amounts of clock time to execute

Many specialized instructions aren’t used frequently

CISC instructions typically set the condition codes as a side effect of the instruction

Question 5

Discuss the operation of a microprocessor, including:

a. List of parts located within the microprocessor.

b. Operation of the control unit (CU).

c. Operation of the arithmetic logic unit (ALU).

A microprocessor, or central processing unit (CPU), is an internal hardware component that performs the mathematical calculations required for computers to run programs and execute commands. Processors are usually made of silicon material that contains tiny electrical components embedded on the surface. Typical computer programs that must be processed by CPUs include Internet browsers, games and video editing software. Everything a computer does is described by lots of precise instructions, and microprocessors carry out these instructions at incredible speed—millions or even billions of times a second.

Microprocessors are used in personal computers, cars, military weapons, and home appliances. Some microprocessors are so small and inexpensive that they are used to control very simple products like flashlights and greeting cards that play music when you open them.

Microprocessor operation

Microprocessors use three steps commonly called Fetch, Decode, and Execute. In the Fetch step, an instruction is copied from the memory of the computer into the microprocessor. In the Decode step, the microprocessor figures out what operation the instruction is meant to do. In the Execute step, this operation is performed.

Operations can be very simple, like adding two numbers, or complicated, like copying a series of letters and numbers (called a string) from one place in the computer's memory to a different place.

A control unit is circuitry that directs operations within the computer's processor by directing the input and output of a computer system. The processor then controls how the rest of the computer operates (giving directions to the other parts and systems). A control unit works by gathering input through a series of commands it receives from instructions in a running program and then outputs those commands into control signals that the computer and other hardware attached to the computer carry out.

The control unit is basically circuitry inside the CPU, controlling the operations inside the CPU and "directing traffic" in a sense. The functions a control unit performs can depend on the type of CPU, since the varying degrees of architecture between all the different CPUs will determine the functions of the control unit.

An arithmetic and logic unit (ALU), in computing, is a digital circuit that performs integer arithmetic and logical operations. The ALU is a fundamental building block of the central processing unit of a computer, and even the simplest microprocessors contain one for purposes such as maintaining timers. The processors found inside modern CPUs and graphics processing units (GPUs) accommodate very powerful and very complex ALUs; a single component may contain a number of ALUs.

Computer machine cycle