Foundations of comp. sci. chapt. 1

Q1-3. What is the role of a program in a computer that is based on the Turing model?

A program is a set of instructions that tells the computer what to do with data. In the Turing model, the output data depends on the combination of two factors: the input data and the program.

What is a computer based on the Turing model?

According to the turing model a computer is a universal computational device (in 1936). He proposed that all computations can be performed by a special kind of a machine, now called a Turing machine.

Define a computer based on the von Neumann model.

According to the von Neumann model, a computer is made up four subsystems which include the memory, the ALU, the control unit and the input/output.

8. What is the function of the control unit subsystem in a computer?

Control unit The control unit controls the operations of the memory, ALU, and the input/output subsystem.

Q1-10. Briefly describe the five generations of computers. First generation

First generation The first generation (roughly 1950-1959) is characterized by the emergence of commercial computers. During this time, computers were used only by professionals. They were locked in rooms with access limited only to the operator or computer specialist. Computers were bulky and used vacuum tubes as electronic switches. At this time, computers were affordable only by big organizations.

Q1-9. What is the function of the input/output subsystem in a computer?

Input / output The input subsystem accepts input data and the program from outside the computer, while the output subsystem sends the result of processing to the outside world. The definition of the input/output subsystem is very broad: it also includes secondary storage devices such as disk or tape that stores data and programs for processing. When a disk stores data that results from processing, it is considered an output device: when it reads data from the disk, it is considered an input device.

Q1-6. What is the function of the memory subsystem in a computer?

Memory Memory is the storage area. This is where programs and data are stored during processing. We discuss the reasons for storing programs and data later in the chapter. Arithmetic logic unit

Second generation

Second-generation computers (roughly 1959-1965) used transistors instead of vacuum tubes. This reduced the size of computers, as well as their cost, and made them affordable to small and medium-size corporations. Two high-level programming languages, FORTRAN and COBOL (see Chapter 9), were invented and made programming easier. These two languages separated the programming task from the computer operation task. A civil engineer, for example could write a FORTRAN program to solve a problem without being involved in the electronic details of computer architecture.

Q1-7. What is the function of the ALU subsystem in a computer?

The arithmetic logic unit (ALU) is where calculation and logical operations take place. For a computer to act as a data processor, it must be able to do arithmetic operations on data (such as adding a list of numbers). It should also be able to do logical operations on data, as we will see in Chapter 4.

Fourth generation

The fourth generation (approximately 1975-1985) saw the appearance of microcomputers. The first desktop calculator, the Altair 8800, became available in 1975. Advances in the electronics industry allowed whole computer subsystems to fit on a single circuit board. This generation also saw the emergence of computer networks (see Chapter 6).

Third generation

The invention of the integrated circuit (transistors, wiring, and other components on a single chip) reduced the cost and size of computers even further. Minicomputers appeared on the market. Canned programs, popularly known as software packages, became available. A small corporation could buy a package, for example for accounting, instead of writing its own program. A new industry, the software industry, was born. This generation lasted roughly from 1965 to 1975.

Q1-4. What is the role of a program in a computer based on the von Neumann model? Q1-5. What are the various subsystems of a computer?

The von Neumann model states that the program must be stored in memory. A program in the von Neumann model is made of a finite number of instructions. In this model, the control unit fetches one instruction from memory, decodes it, then executes it. Memory, ALU, CU and Input or Output

Fifth generation

This open-ended generation started in 1985. It has witnessed the appearance of laptop and palmtop computers, improvements in secondary storage media (CD-ROM, DVD, and so on), the use of multimedia, and the phenomenon of virtual reality.