Introduction to Digital Computers

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Questions and Answers

What role do computers play in executing algorithms or programs?

Obtaining solutions for problems

How do analog computers represent information?

By physical quantities that can take values from a continuum

What are the limitations of early computers?

They were susceptible to environmental factors

How do modern computers combat the effect of electrical noise and other environmental effects?

By using error-correcting codes and other fault tolerance measures Signup and view all the answers

What is an example of analog-data representation?

The electrical signals on a telephone line Signup and view all the answers

How do analog computers perform operations?

Using the physical characteristics of its data Signup and view all the answers

What was the motivation behind the development of analog computers?

To directly model the smoothly varying properties of physical systems Signup and view all the answers

What advantage do analog computers have over digital computers?

They can often avoid time-consuming arithmetic and logical operations Signup and view all the answers

What was the most significant concept introduced in the 1940s that changed the way computers operate?

Storing programs as data Signup and view all the answers

What is a characteristic of stored program computers?

They can execute different programs one after the other Signup and view all the answers

What can a program do in a stored program computer?

Manipulate another program as data Signup and view all the answers

What is the role of compilers and assemblers?

To translate programs from high-level languages to machine language Signup and view all the answers

What is the purpose of the compilation process?

To translate the program into machine language Signup and view all the answers

What type of errors are detected during the compilation process?

Syntax errors Signup and view all the answers

What is the result of correcting syntax errors?

The program is re-compiled Signup and view all the answers

What is the final step in solving a problem using a computer?

Program execution Signup and view all the answers

What is the purpose of the stored program concept?

To allow programs to be stored and transferred like data Signup and view all the answers

What is the significance of the stored program concept in modern computers?

It is the basis for virtually every general-purpose computer Signup and view all the answers

What is a major limitation of analog computers?

Their susceptibility to errors due to changes in temperature and humidity Signup and view all the answers

What is the primary advantage of digital computers over analog computers?

Their resilience to errors Signup and view all the answers

What is the fundamental unit of information in digital computers?

Bit Signup and view all the answers

Why do digital computers use a binary system?

Because it is the simplest system to implement Signup and view all the answers

What is the purpose of error-correcting features in digital computers?

To combat the effects of electrical noise Signup and view all the answers

How are different types of information represented in digital computers?

Using concatenations of bits called bit patterns Signup and view all the answers

What is the default meaning of the term 'computer' today?

A general-purpose automatic electronic digital computer Signup and view all the answers

How were programs conveyed to early computers?

Using plug boards Signup and view all the answers

What was a major limitation of early computers that used plug boards?

The need to rewire the system for each new program Signup and view all the answers

What is the primary advantage of the stored program concept in digital computers?

It allows for easier modification of programs Signup and view all the answers

What is the typical application of a Disposable computer?

Greeting cards, watches Signup and view all the answers

What is the price range of a Desktop or laptop PC?

$1000 Signup and view all the answers

What is a typical application of a Supercomputer?

Weather forecast, oil exploration Signup and view all the answers

What is a common consideration when deciding which computer system to purchase?

Software and object code compatibility Signup and view all the answers

What is at the high end of the computer spectrum?

Supercomputer Signup and view all the answers

What are the two essential parts of a program?

Instructions and data Signup and view all the answers

What is the primary function of an operating system?

To provide a uniform software interface to hardware resources Signup and view all the answers

What is the purpose of a hardware timer in a multitasking environment?

To interrupt the running program and allow the processor to run the operating system Signup and view all the answers

What is the primary goal of the operating system in multitasking environments?

To minimize processor waste time Signup and view all the answers

What is the function of memory management in an operating system?

To support a large virtual memory address space with a much smaller physical memory Signup and view all the answers

What happens when a peripheral device interrupts the running program?

The operating system intervenes and services the devices Signup and view all the answers

What is the relationship between software and hardware in a computer system?

Software is only productive when executed on suitable hardware with proper data Signup and view all the answers

What is the purpose of exception handling in an operating system?

To handle situations that cause unexpected events such as arithmetic overflow and divide by zero Signup and view all the answers

What is the role of the operating system in a computer system?

To provide a standard interface to system resources and support sharing among concurrently executing programs Signup and view all the answers

What is the main difference between user programs and kernel programs?

Kernel programs are part of the operating system, while user programs are not Signup and view all the answers

What is the central component that controls and coordinates the actions performed by the computer?

Central Processing Unit (CPU) Signup and view all the answers

What is the primary function of the input unit?

To accept information from human users or other machines Signup and view all the answers

What is stored in the memory unit?

Both the instructions and data of the program being executed Signup and view all the answers

What is the main similarity between the digital computer and the human information processing system?

The way information is input and output Signup and view all the answers

How does the human information processing system store information?

Through internal connectivity Signup and view all the answers

What is the primary function of the output unit?

To provide output to the outside world Signup and view all the answers

What is software in the context of computer systems?

Abstract ideas, algorithms, and their computer representations Signup and view all the answers

What is the relationship between software and hardware in computer systems?

They are intimately tied together Signup and view all the answers

What is the function of the control unit in the CPU?

To behave like a puppeteer who pulls the right strings to make the puppets behave exactly as needed Signup and view all the answers

How does information processing happen in a digital computer?

By bringing small pieces from the memory into the CPU and processing Signup and view all the answers

What is the main idea behind the concept 'Hardware is petrified software'?

Any operation performed by software can also be built directly into the hardware Signup and view all the answers

What is the primary reason for implementing certain functions in hardware and others in software?

Based on factors such as cost, speed, reliability, and frequency of expected changes Signup and view all the answers

What is the main difference between a desktop computer and an entertainment PC?

The quality of graphics, video, and audio they support Signup and view all the answers

What is a server in the context of computer systems?

A high-performance computer that serves as a gateway Signup and view all the answers

What is the main characteristic of computers used in applications such as automobiles and home appliances?

They are embedded computers Signup and view all the answers

What is the main similarity between all computers, regardless of their size and purpose?

They all have the same general principles of computer architecture and organization Signup and view all the answers

What is the main reason why disposable computers are inexpensive?

They use a single chip with small amounts of memory and are produced in large quantities Signup and view all the answers

What is the main difference between a computer program and an electronic circuit?

A computer program can be simulated in software, while an electronic circuit is built directly into the hardware Signup and view all the answers

What is the main implication of the concept that 'Any operation performed by software can also be built directly into the hardware'?

There is no fundamental difference between hardware and software Signup and view all the answers

What is the main reason why researchers are developing computers made from quantum circuits and biological circuits?

To explore new computation models and improve computer performance Signup and view all the answers

Study Notes

The Digital Computer

The digital computer plays a major role in executing algorithms or programs to obtain solutions for problems.
Solving a problem involves manipulating information of one kind or other.
Computers internally represent information by some means, which can be either analog or digital.

Analog Computers

Early computers were analog computers that represented information by physical quantities that can take values from a continuum.
Examples of analog quantities include rotational positions of gears in mechanical computers and voltages in electrical computers.
Analog computers use the physical characteristics of their data to determine solutions.
They can nicely represent smoothly changing values and make use of their properties.

Limitations of Analog Computers

Analog computers suffer from the difficulty in measuring physical quantities precisely.
They are also affected by changes in temperature, humidity, and other environmental factors.
The subtle errors introduced to the stored values due to such noise are difficult to detect and correct.

Digital Computers

Digital computers represent and manipulate information using discrete elements called symbols.
A major advantage of using symbols is resilience to error.
Digital computers use distinct voltage states (or current states) to represent different symbols.
Each switch can be in one of two positions, on or off, making it easiest for digital circuits to handle only two symbols.

Binary System

Most digital computers use only two symbols in their alphabet and are binary systems.
The two symbols of the computer alphabet are usually represented as 0 and 1, each symbol is called a binary digit or a bit.
Computers often need to represent different kinds of information, such as instructions, integers, floating-point numbers, and characters, which are represented by concatenations of bits called bit patterns.

The Stored Program Concept

The stored program concept was first described in a landmark paper by Burks, Goldstein, and von Neumann in 1946.
In a digital computer implementing the stored program concept, a program is a collection of bit patterns.
The stored program concept allows programs to be stored and transferred like data, and enables computers to be easily adapted to do different types of computational and information storage tasks.

Basic Steps in Solving a Problem using a Computer

The basic steps in solving a problem using a computer are:
- Developing an algorithm to solve the problem.
- Expressing the algorithm as a program in a high-level programming language.
- Translating the source program into an executable program using programs such as compilers, assemblers, and linkers.
- Executing the program with a set of input values to obtain the results.

Basic Software Organization

The software consists of symbols or bit patterns that can be stored in storage devices.
A program consists of two parts: instructions and data, both of which are represented by bit patterns.
The instructions indicate specific operations to be performed on individual data items.
The operating system is a supervisory program that regulates access and control of hardware resources.

Basic Hardware Organization

The basic hardware organization of a digital computer consists of three functionally independent parts: the CPU (central processing unit), the memory unit, and the input/output unit.
The CPU executes a memory-resident program by reading the program instructions and data from the memory.
The input/output unit is a collection of diverse devices that enable the computer to communicate with the outside world.

Software vs Hardware

Software consists of abstract ideas, algorithms, and their computer representations, namely programs.
Hardware, in contrast, consists of tangible objects such as integrated circuits, printed circuit boards, cables, power supplies, memories, and printers.
The boundary between the software and the hardware is of particular interest to systems programmers and compiler developers.

Computer Platforms

Computers come in various sizes, speeds, and prices, from small-scale to large-scale.
The categorization of computers is somewhat idealized, and within each category, there is wide variability in features and cost.
The approximate price figures are only intended to show order of magnitude differences between different categories.### Computer Architecture and Organization
The principles of computer architecture and organization are the same for all types of computers, from small embedded systems to large distributed systems.

Types of Computers

Disposable computers: used in applications like greeting cards and watches, costing around $1, with a single chip and small memory, produced in large quantities.
Embedded computers: used in applications like home appliances and cars, costing around $10.
Entertainment PCs: optimized for games, personal communications, and video playback, with high-quality graphics, video, and audio, costing around $100.
Desktop and laptop PCs: intended for single users, running applications like word processing, web browsing, and email, with varying features and costs, around $1000.
Servers: high-performance computers serving as gateways in a network, costing around $10,000.
Collection of workstations: a group of computers, costing around $100,000.
Mainframes: used for applications like bank accounts and airline reservations, costing around $1,000,000.
Supercomputers: used for complex calculations, such as weather prediction and nuclear explosion modeling, costing around $10,000,000.

Key Considerations

The lower end of the spectrum often provides the best price/performance ratio.
The decision on which system to purchase is often influenced by software and object code compatibility.

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