Exam 1 Vocabulary

algorithm

A step-by-step process for solving a category of problems.

counter

A variable used to count something, usually initialized to zero and incremented in the body of a loop.

cursor

An invisible marker that keeps track of where the next character will be printed.

development plan

A process for developing a program. In this chapter, we demonstrated a style of development based on developing code to do simple, specific things and then encapsulating and generalizing.

encapsulate

To divide a large complex program into components (like functions) and isolate the components from each other (by using local variables, for example).

escape sequence

An escape character, \\, followed by one or more printable characters used to designate a nonprintable character.

generalize

To replace something unnecessarily specific (like a constant value) with something appropriately general (like a variable or parameter). Generalization makes code more versatile, more likely to be reused, and sometimes even easier to write.

increment

Both as a noun and as a verb, increment means to increase by 1.

infinite loop

A loop in which the terminating condition is never satisfied.

initialization (of a variable)

To initialize a variable is to give it an initial value, usually in the context of multiple assignment. Since in Python variables don’t exist until they are assigned values, they are initialized when they are created. In other programming languages this is not the case, and variables can be created without being initialized, in which case they have either default or garbage values.

iteration

Repeated execution of a set of programming statements.

loop

A statement or group of statements that execute repeatedly until a terminating condition is satisfied.

loop variable

A variable used as part of the terminating condition of a loop.

multiple assignment

Making more than one assignment to the same variable during the execution of a program.

newline

A special character that causes the cursor to move to the beginning of the next line.

tab

A special character that causes the cursor to move to the next tab stop on the current line.

trace

To follow the flow of execution of a program by hand, recording the change of state of the variables and any output produced.

exception

An error that occurs at runtime.

handle an exception

To prevent an exception from terminating a program using the try and except statements.

raise

To signal an exception using the raise statement.

bug

An error in a program.

byte code

An intermediate language between source code and object code. Many modern languages first compile source code into byte code and then interpret the byte code with a program called a virtual machine.

compile

To translate a program written in a high-level language into a low-level language all at once, in preparation for later execution.

debugging

The process of finding and removing any of the three kinds of programming errors.

exception

Another name for a runtime error.

executable

Another name for object code that is ready to be executed.

formal language

Any one of the languages that people have designed for specific purposes, such as representing mathematical ideas or computer programs; all programming languages are formal languages.

high-level language

A programming language like Python that is designed to be easy for humans to read and write.

interpret

To execute a program in a high-level language by translating it one line at a time.

low-level language

A programming language that is designed to be easy for a computer to execute; also called machine language or assembly language.

natural language

Any one of the languages that people speak that evolved naturally.

object code

The output of the compiler after it translates the program.

parse

To examine a program and analyze the syntactic structure.

portability

A property of a program that can run on more than one kind of computer.

print statement

An instruction that causes the Python interpreter to display a value on the screen.

problem solving

The process of formulating a problem, finding a solution, and expressing the solution.

program

a sequence of instructions that specifies to a computer actions and computations to be performed.

Python shell

An interactive user interface to the Python interpreter. The user of a Python shell types commands at the prompt (>>>), and presses the return key to send these commands immediately to the interpreter for processing.

runtime error

An error that does not occur until the program has started to execute but that prevents the program from continuing.

script

A program stored in a file (usually one that will be interpreted).

semantic error

An error in a program that makes it do something other than what the programmer intended.

semantics

The meaning of a program.

source code

A program in a high-level language before being compiled.

syntax

The structure of a program.

syntax error

An error in a program that makes it impossible to parse — and therefore impossible to interpret.

token

One of the basic elements of the syntactic structure of a program, analogous to a word in a natural language.

argument

A value provided to a function when the function is called. This value is assigned to the corresponding parameter in the function.

body

the block of statements in a compound statement that follows the header

compound statement

A statement that consists of two parts:

header - which begins with a keyword determining the statement type, and ends with a colon.
body - containing one or more statements indented the same amount from the header.

The syntax of a compound statement looks like this:

keyword expression:
statement
statement ...

flow of execution

The order in which statements are executed during a program run.

frame

A box in a stack diagram that represents a function call. It contains the local variables and parameters of the function.

function

A named sequence of statements that performs some useful operation. Functions may or may not take parameters and may or may not produce a result.

function call

A statement that executes a function. It consists of the name of the function followed by a list of arguments enclosed in parentheses.

function composition

Using the output from one function call as the input to another.

function definition

A statement that creates a new function, specifying its name, parameters, and the statements it executes.

header

The first part of a compound statement. Headers begin with a keyword and end with a colon (:)

import

A statement which permits functions and variables defined in a Python script to be brought into the environment of another script or a running Python shell.

local variable

A variable defined inside a function. A local variable can only be used inside its function.

parameter

A name used inside a function to refer to the value passed as an argument.

stack diagram

A graphical representation of a stack of functions, their variables, and the values to which they refer.

traceback

A list of the functions that are executing, printed when a runtime error occurs. A traceback is also commonly refered to as a stack trace, since it lists the functions in the order in which they are stored in the runtime stack.

assignment operator

= is Python’s assignment operator, which should not be confused with the mathematical comparison operator using the same symbol.

assignment statement

a statement that assigns a value to a name (variable). to the left of the assignment operator =, is a name.

comment

Information in a program that is meant for other programmers (or anyone reading the source code) and has no effect on the execution of the program.

composition

The ability to combine simple expressions and statements into compound statements and expressions in order to represent complex computations concisely.

concatenate

To join two strings end-to-end.

data type

A set of values. The type of a value determines how it can be used in expressions. So far, the types you have seen are integers (type int), floating-point numbers (type float), and strings (type str).

evaluate

To simplify an expression by performing the operations in order to yield a single value.

expression

A combination of variables, operators, and values that represents a single result value.

float

A Python data type which stores floating-point numbers. Floating-point numbers are stored internally in two parts: a base and an exponent. When printed in the standard format, they look like decimal numbers. Beware of rounding errors when you use floats, and remember that they are only approximate values.

int

A Python data type that holds positive and negative whole numbers.

integer division

An operation that divides one integer by another and yields an integer. Integer division yields only the whole number of times that the numerator is divisible by the denominator and discards any remainder.

keyword

A reserved word that is used by the compiler to parse program; you cannot use keywords like if, def, and while as variable names.

operand

One of the values on which an operator operates.

operator

A special symbol that represents a simple computation like addition, multiplication, or string concatenation.

rules of precedence

The set of rules governing the order in which expressions involving multiple operators and operands are evaluated.

state diagram

A graphical representation of a set of variables and the values to which they refer.

statement

An instruction that the Python interpreter can execute. Examples of statements include the assignment statement and the print statement.

str

A Python data type that holds a string of characters.

value

A number or string (or other things to be named later) that can be stored in a variable or computed in an expression.

variable

A name that refers to a value.

variable name

A name given to a variable. Variable names in Python consist of a sequence of letters (a..z, A..Z, and _) and digits (0..9) that begins with a letter. In best programming practice, variable names should be chosen so that they describe their use in the program, making the program self documenting.

argument

A value provided to a function when the function is called. This value is assigned to the corresponding parameter in the function.

body

The second part of a compound statement. The body consists of a sequence of statements all indented the same amount from the beginning of the header. The standard amount of indentation used within the Python community is 4 spaces.

compound statement

A statement that consists of two parts:

header - which begins with a keyword determining the statement type, and ends with a colon.
body - containing one or more statements indented the same amount from the header.

The syntax of a compound statement looks like this:

keyword expression:
statement
statement ...

flow of execution

The order in which statements are executed during a program run.

frame

A box in a stack diagram that represents a function call. It contains the local variables and parameters of the function.

function

A named sequence of statements that performs some useful operation. Functions may or may not take parameters and may or may not produce a result.

function call

A statement that executes a function. It consists of the name of the function followed by a list of arguments enclosed in parentheses.

function composition

Using the output from one function call as the input to another.

function definition

A statement that creates a new function, specifying its name, parameters, and the statements it executes.

header

The first part of a compound statement. Headers begin with a keyword and end with a colon (:)

import

A statement which permits functions and variables defined in a Python script to be brought into the environment of another script or a running Python shell.

local variable

A variable defined inside a function. A local variable can only be used inside its function.

parameter

A name used inside a function to refer to the value passed as an argument.

stack diagram

A graphical representation of a stack of functions, their variables, and the values to which they refer.

traceback

A list of the functions that are executing, printed when a runtime error occurs. A traceback is also commonly refered to as a stack trace, since it lists the functions in the order in which they are stored in the runtime stack.

boolean function

A function that returns a boolean value.

composition (of functions)

Calling one function from within the body of another, or using the return value of one function as an argument to the call of another.

dead code

Part of a program that can never be executed, often because it appears after a return statement.

fruitful function

A function that yields a return value.

incremental development

A program development plan intended to avoid debugging by adding and testing only a small amount of code at a time.

None

A special Python value returned by functions that have no return statement, or a return statement without an argument. None is the only value of the type, NoneType.

return value

The value provided as the result of a function call.

scaffolding

Code that is used during program development but is not part of the final version.

temporary variable

A variable used to store an intermediate value in a complex calculation.

unit testing

An automatic procedure used to validate that individual units of code are working properly. Python has doctest built in for this purpose.

block

A group of consecutive statements with the same indentation.

body

The block of statements in a compound statement that follows the header.

boolean expression

An expression that is either true or false.

boolean value

There are exactly two boolean values: True and False. Boolean values result when a boolean expression is evaluated by the Python interepreter. They have type bool.

branch

One of the possible paths of the flow of execution determined by conditional execution.

chained conditional

A conditional branch with more than two possible flows of execution. In Python chained conditionals are written with if ... elif ... else statements.

comparison operator

One of the operators that compares two values: ==, !=, >, <, >=, and <=.

condition

The boolean expression in a conditional statement that determines which branch is executed.

conditional statement

A statement that controls the flow of execution depending on some condition. In Python the keywords if, elif, and else are used for conditional statements.

logical operator

One of the operators that combines boolean expressions: and, or, and not.

modulus operator

An operator, denoted with a percent sign ( %), that works on integers and yields the remainder when one number is divided by another.

nesting

One program structure within another, such as a conditional statement inside a branch of another conditional statement.

prompt

A visual cue that tells the user to input data.

type conversion

An explicit statement that takes a value of one type and computes a corresponding value of another type.

wrapping code in a function

The process of adding a function header and parameters to a sequence of program statements is often refered to as “wrapping the code in a function”. This process is very useful whenever the program statements in question are going to be used multiple times.

abstraction

Generalization by reducing the information content of a concept. Functions in Python can be used to group a number of program statements with a single name, abstracting out the details and making the program easier to understand.

constant

A numerical value that does not change during the execution of a program. It is conventional to use names with all uppercase letters to repesent constants, though Python programs rely on the discipline of the programmers to enforce this, since there is no language mechanism to support true constants in Python.

nested loop

A loop inside the body of another loop.

random

Having no specific pattern. Unpredictable. Computers are designed to be predicatable, and it is not possible to get a truly random value from a computer. Certain functions produce sequences of values that appear as if they were random, and it is these psuedorandom values that we get from Python.

trichotomy

Given any real numbers a and b, exactly one of the following relations holds: a < b, a > b, or a = b. Thus when you can establish that two of the relations are false, you can assume the remaining one is true.

Exam 1 Vocabulary

Computer Applications 1301 with Summet at Georgia Institute of Technology

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