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.