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Chapter 5

Information System Software

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Software Concepts A program is a set of instructions that

tells the computer what to do. Software can be a single program or a

group of programs needed to perform several functions.

Simple programs may have a few hundred instructions (lines of code) though most have many more (several million).

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Individual Application Software Word processing Spreadsheet Graphics Database Browser

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Workgroup Application Software Groupware

E-Mail software Electronic conferencing software

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Other Application Software Organizational application software

Generally organization specific Examples include payroll, account payable.

Interorganizational application software Generally common to the participating

organizations Electronic Data Interchange (EDI) Electronic Funds Transfer (EFT)

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Operating System Concepts An operating system is a group of

programs that manages the operation of the computer.

Three functions of an operating system Operation (Process) management Resource management Data management

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Operating System Concepts (cont’d.) Organization of an operating

system Most operating system programs are

stored in secondary storage. One operating system program is

stored in a section of primary storage. It goes by various names – kernel, nucleus, core, … – but generically called the “supervisor”.

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Using an Operating System Starting the computer is called booting

which transfers the “supervisor” from secondary storage to primary storage.

Connecting to a network or other multi-user environment is called logging in.

Detaching from a network is called logging out.

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Elements of an Operating System’s User Interface User interface is the visual link between

the user and the software. Icons are the small pictures on the

screen. Graphical User Interface (GUI) uses

Buttons (radio buttons, check boxes) Icons Menus Dialog boxes

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Capabilities of Operating Systems Multitasking is appearing to

execute more than one program at a time, though the CPU can execute instructions from only one program at a time.

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Capabilities of Operating Systems (cont’d.) Multi-user or Multiple-user systems

permit more than one person to use the system at a time.

The technique that is used with multiple-user operating systems is time sharing. With this technique, the users are each allocated a small amount of time by the operating system.

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Capabilities of Operating Systems (cont’d.) Two types of operating systems

Batch operating systems where all the transactions belong to a program are processed at the same.

Interactive operating systems allow user interaction as the program executes. In this method of processing one transaction is performed at the time, so the user can correct the errors.

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Capabilities of Operating Systems (cont’d.) Virtual memory is supplemental

primary storage (RAM) or “real” memory where the programs are too big for primary storage. It is created on a secondary storage device.

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Capabilities of Operating Systems (cont’d.) Virtual memory operating systems

execute large programs by dividing the program into parts and transferring the necessary parts of the program from secondary storage to primary storage as needed.

The transfer process does not require any action by the user.

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Other System Software Utility programs

Sort utility – rearranges data in a specified order

Merge utility – merges two files into one

Print utility – prints the contents of a file

Copy utility – copies data from one device to another

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Other System Software (cont’d.) Communications software – used

for communications between computers.

Database management software – used for managing databases.

Software development software – software used to develop software.

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What is a Programming Language

English is a natural language. It has words, symbols and grammatical rules.

A programming language also has words, symbols and rules of grammar.

The grammatical rules are called syntax. Each programming language has a

different set of syntax rules.

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Why Are There So Many Programming Languages Programming languages have

evolved over time as better ways have been developed to design them.

Different programming languages are designed for different types of programs.

First programs were developed in the 1950s.

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What Are the Types of Programming Languages First Generation Languages Second Generation Languages Higher Generation Languages

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First Generation Languages

Machine language Operation code – such as addition or

subtraction. Operands – that identify the data to be

processed. Machine language is machine dependent

as it is the only language the computer can understand.

Very efficient code but very difficult to write.

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Second Generation Languages

Assembly languages Symbolic operation codes replaced

binary operation codes. Assembly language programs needed to

be “assembled” for execution by the computer. Each assembly language instruction is translated into one machine language instruction.

Very efficient code and easier to write.

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Higher Generation Languages

Closer to English. Less Efficient.

Because Programs written in source code which must be translated into machine language programs called object code.