Chapt 1 Introduction to Computer Programming

Compiler

a program used in the translation process of translating instructions into machine language. this program translates each instruction into one or more machine language instructions

Machine independent

third-generation instruction that might be converted into more than one machine-language instruction that is not tied to particular computers

Systems analyst

this person who works on a particular project provides specifications to be used by the programmer.

Statement

all programming languages consist of a set of these instructions and syntax rules for putting them together to make valid instructions

Register

a special storage area in the ALU where all calculations are done

Graphical user interface (GUI)

an easy-to-use interface with which a user can interact. it contains buttons, menus, and scroll bars. this interface is common to all applications written for Windows environment

User

analysts develop specifications by working with this person or persons who will be using the program when it is complete in order to determine how best to solve a problem or improve operations

Character (string) field

any nonnumeric field is a character, or string, field

Firmware

computer programs actually built into the hardware Example. the instructions built into the ROM of a microcomputer to start the computer when it is turned on

Assembler program

computer programs that translate assembly language programs into machine language

Date field

consists of a calendar date Example. "Date money turned in"

Application software

consists of the programs that carry out business functions, such as inventory, payroll, and so on

Real (floating point) field

refer to numeric fields that have decimal points such as 11.213 and -12.36. can be single precision or double precision depending on the magnitude and accuracy required

Nonnumeric (alphanumeric) field

contain any character including numbers, letters of the alphabet, and special characters such as dollar signs ($), percent signs (%), hyphens (-), and commas (,)

Numeric field

contain only numbers, a decimal point, a positive or negative sign

Field (data) type

describes the type of data contained in the field. fields can be numeric or nonnumeric

Character (byte)

fields are composed of characters. the binary digits used to represent a character are called a byte. Exampel. In the NAME field that contains the name SAMUEL JOHNSON, there are 14 characters: S A M U E L J O H N S O N including the space or blank between the first and last names.

Third-generation language

includes FORTRAN, COBOL, C, C++, BASIC, AND Visual BASIC

Machine language

the binary (on/off) representation of computer instructions

Hardware

the physical devices used to process data Example. a computer

Debugging

the process of testing a program and finding and correcting errors

Source program

the program written by the programmer which is the input to a compiler, interpreter, or assembler

Translate a program

translating assembly language instructions into machine language (binary code)

Manual Data Processing

processing data without a computer

Data

raw facts Example. a list of test scores, a stack of bills, or a recipe

Secondary (external or auxiliary) storage

used as additional memory for the computer, is cheaper than primary storage because it does not have to be as fast. it is permanent in that turning off the computer does not erase secondary storage. Example. magnetic disks and tapes and compact disks, as well as ZIP disks

Mnemonics

words and symbols used in assembly language

Assembly language

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Logical (boolean) field

contains one of two values such as "yes"/"no" or "true"/"false" Example. "Money turned in to the league"

File

data related to a particular subject organized in secondary storage

Information

data that have been processed and made useful

Operand

describes the data used in the instruction

Programming Logic

designing solutions to problems that will be solved by a computer

Operation Code

machine language instructions that consist of the instruction to be executed

System software

software, such as the operating system, is needed to make the computers usable. the operating system communicates with hardware to accomplish input and output functions. Example. Windows 2000 (an Operating System)

ROM (read-only memory)

special type of main memory that cannot be changed by the programmer. it contains instructions for doing such things as starting up the computer when you turn it on. these instructions are built into a memory chip and cannot be erased when the power to the computer is turned off. the programmer has no control over what is stored in the ROM

Primary (main) storage (memory)

stores the data and instructions (programs) needed by the computer

Software

term used to describe computer programs

Database

a collection of one or more related files Example. phone directory files, records, fields, characters, and bits

Field (data item, variable)

a group of consecutive storage positions reserved for a particular type of data (records are composed of fields) Ex. name, address, phone number, and Social Security number

Computer Program

a sequence of instructions that machines are capable of following

Subroutine (function or module)

a set of instructions or tasks that accomplishes a specific function of the program Example. printing heading on a report, accessing a file, or doing a complicated calculation

Binary digit (bit)

characters are composed of binary digits (bits) 0 and 1

Machine dependent

means that each computer had its own machine language, so a program written for a particular computer would not work on another type of computer

Computer Programmer

people who write computer programs

Control unit

thought of as the "brain" of the computer. among other things, it determines which program instruction to execute, interprets the instruction, and causes the instruction to be executed

C

was developed by Dennis Ritchie at Bell Laboratories in the early 1970s, is used extensively for systems programs because it gives the programmer a lot of control over hardware. the UNIX operating system was written in C. many applications programs such as word processors, spreadsheets, are also written in C

COBOL (COmmon Business-Oriented Language)

was developed by a group of computer professionals in 1959. it is used primarily for business applications. these programs are divided into four divisions. the Identification Division documents the program and provides identifying information to the computer. the Environment Division names the computer hardware. the Data Division specifies the files and data used by the program.

BASIC (Beginner's All-purpose Symbolic Instruction Code)

was developed in the mid-1960s at Dartmouth College by John Kemeny and Thomas Kurtz to allow students to write simple interactive programs. there have been many versions of BASIC. Visual BASIC, the newest version of BASIC, is an object-oriented, event-driven programming language

Object-oriented language

when programming in this language, the programmer creates objects and methods for working with the objects. one of the first object-oriented programming languages was Smalltalk, which was developed in the mid-1970s by Xerox Corporation. Example. C++

Data Organization

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Second-generation language

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Integer field

a numeric field that contains a whole number that is positive, negative, or zero. integers can be short integers or long integers depending on their magnitude and can be signed (stored with a positive or negative sign) or unsigned (positive or zero only) Example. -1, 0, and 25

Interpreter

a program used in the translation process of translating instructions into machine language. this program translates each instruction into one or more machine language instructions

Documentation

a written commentary of the programming process. it should include such things as the specifications provided by the analyst, flowcharts and other planning aids, a list of the source program, comments in the program, sample test data, and test results

Code a program

after the solution is planned, the next step is to write a source program for the solution in a programming language such as Assemble, COBOL, Visual BASIC or C++

Object program

compilers and assemblers generate this machine language as output

Variant field

contains any type of data ***Programmers must be very careful when attempting to do arithmetic with variant fields

Input/ output (I/O) device (peripheral)

hardware used to get data and instructions from secondary to primary storage and vice versa Example. disk drives, CD-ROM drives, tape drives, keyboards, mice, printers, and video displays

Fourth-generation (4GL) language

high-level languages that require much less programmer effort than third-generation languages. they are typically used to retrieve information from files and databases INCLUDE: SQL (a common query language), report generators, form designers, and application generators

Record

how files are composed Example1. each listing in a phone directory represents a record (files are composed fo records) Example 2. a payroll file contains one record for each employee

Field Name (data name, variable, identifier)

identifies the field and provides a name to access the data contained in the field

Procedure-oriented language

in these languages, the emphasis of the program is on how to accomplish a task. the programmer writes the instructions as well as determines the order in which the computer should process the instructions Example. FORTRAN, COBOL, BASIC, and C

Execute a program

instructions must first be taken from the secondary storage medium on which they are kept and loaded (put) into the primary storage of the computer

Event-driven, visual language

languages that simplified the task of programming applications for Windows. in these languages, the emphasis of a program is on the objects (ex. buttons) included in the user interface and the events (such as clicking a mouse button) that occur when these objects are used. the goal is to give the user as much control over the program as possible Example. Visual C++, Visual BASIC

RAM (random-access memory)

main memory. before a program's instructions can be carried out or executed by the computer, these instructions must be stored in RAM.

Translation (syntax or language) error

output includes a list of diagnostics that show these errors Examples. using a field name that contains too many characters, misspelling a computer instruction, branching to a nonexistent location in your program, and violating the punctuation rules of a language

Arithmetic/ logic unit (ALU)

responsible for doing arithmetic computations (for example, ADD A TO B), data transfers (moving data from one area of storage to another), and logical comparisons (such as IS A = 3?) as directed by the control unit

Logic error

results that are not correct because of using an incorrect operation by the computer

Syntax

rules used for programming languages in software. if a programmer makes a syntax error in a programming language, the computer cannot understand what to do, and an error results

System

the analyst studies this current collection of people, machines, and procedures that work together to accomplish objectives to find out what input, processing, and output procedures are currently being used

First-generation languages

the earliest programmers wrote instructions in machine. when computers were first invented, this was the only type of programming language available. machine language instructions are written in binary (series of 0s and 1s)

FORTRAN (FORmula TRANslation)

the first widely used third-generation, high-level programming language. it was developed at IBM Corporation in the mid-1950s and has been enhanced many times since then. it is commonly used for mathematical, scientific, and engineering applications

Computer system

the interconnected devices capable of processing data, which have been input, and supplying the resulting information as output. consists of input devices, output devices, and a processing device

Program testing

the only way to find logic errors

Central processing unit (CPU)

the processing device used by a computer. consists of a control unit and an arithmetic/logic unit. together with primary storage, the CPU does the processing functions of the computer system

Program specifications

the specifications used by the programmer

Memory size of a computer

the storage capacity of its RAM. measured in kilobytes (K). a single kilobyte is 1,024 storage locations. one thousand kilobytes is equivalent to 1 megabyte, and 1,000 megabytes is equivalent to 1 gigabyte

High-level language

these languages require much less programmer effort because they are more English-like and require fewer instructions.