4080 Midterm

simplicity

language with a minimal set of features, with rules on how to apply them and combine them as simply and clearly as possible

orthogonality

the way different constructs can be combine, and how simple these combinations are to understand

level of abstraction

the features provided to create abstractions (C=simple with low lv of ab. while Java=not simple with high lv of ab)

portability

to what degree can the program created in the language be moved from one system to another

cost

cost of using the language in a project (development, compilation, maintenance, execution)

expressivity

how easy it is to come up with different solutions to a problem

von neuman architecture

most common form of computer architecture on modern machines

compiler

take source code and turn it into machine code

interpreter

program that takes source code and executes it

virtual machine

code is compiled into byte code (instructions are sent to a simulated computer)

syntax

how we create the program

lexicon

alphabet, rules for names, reserved words, case sensitive

grammar

rules to create valid sentences

semantics

the meaning of what is used to create the program

variable

a name of a memory location of a particular data type that can be destructively updated

binding

connection between a name and a property

memory binding

(memory allocation) process of reserving and associating with a name

static memory allocation

memory is allocated before execution by the compiler (fast runtime)

dynamic memory allocation

memory is allocated while program is running (overhead when finding memory during runtime)

process memory block

stack/heap/data/text

type binding

association of a name to a type (lexical/syntactic/semantic/translation/optimization/transcription)

static typing

name are assigned a type before the program is run

dynamic typing

name is assigned a type while the program is running

explicit vs implicit typing

if the language requires the use of a syntactic feature to specify the type then the language is explicit

scope bind

process of associating a name with he a scope

scope

region/block area in the code where names are visible

static scope

(lexical scoping) the scope of a name is defines while the code is being written with lexical features

dynamic scoping

visibility of names is determined during run time by looking at the stack activation records.

symbol table

symbol/l-value: value of the memory location that will hold the variable you want to store/r-value: actual value you want to store

expression

sequence of symbols that yields a value (arithmetic / boolean)

arithmetic expression

deals with numbers

boolean expression

deals with relational and logical expressions

operator

a syntactic feature in a language that represents a function that takes input and produces a value

unary

deals with 1 operand ex: !

binary

deals with 2 operands

ternary

deals with 3 operands ex: ?

N-ary

deals with N amount of operands

prefix

operator is place before the operands ex: + 3 4

infix

operator is place between the operands ex: 3 + 4

suffix

operator is place after the operands ex: x++

type

the … of a name is a property that describes the nature of the data associated with the name, and how it should be handled

primitive type

part of the definition of the language, not made of other types, atomic (int, float, char, bool)

user defined type

a type created by a user, mechanism used to create this type is high complexity can go from simple enumeration to abstract data types ADT

arithmetic expression

any expression that yields a numerical type ( + , - , / , ** , % )

order of evaluation

in what order are operands evaluated L>R or R>L

precedence

a mechanism to sort ambiguous expressions by creating hierarchy of operands where the position of the hierarchy determines the relative binding strength of the operator (1. expo 2. mod 3. mul/dif 4. add/sub)

parentheses

if order of evaluation and precedence yields an expression with semantics different from desired, this can be used to override and impose a particular order of operation

side effect

an expression is said to be … free (aka pure) if the evaluation results in visual change (destructive update) in memory

referential transparency

if substitution if the expression but the value it yields results in a program with the same semantics then it is…

overloading of operands

if the operand performs more than one function depending on the type ex: in java, + can be used: (int + int)addition or (str + str)concatenation

type conversion

when a program requires to convert a numerical type into another

type coercion

conversion is implicit / automatic

casting

(explicit type coercion) conversion is explicit and performed with syntactic features from the language

mixed-mode expression

an expression where then is more than one type of operand

overflow

when an arithmetic expression results in a number greater than the maximum representable number in the current data format

underflow

occurs then a floating point operation results in a number that is less than the minimum representable number (mantissa + exponent)

relational expression

greater than, less than, equal to, not equal to

logical expression

and, or, not , implication

short-circuit evaluation

lazy evaluation which given a logical operation, if the evaluation of the first operand is enough to determine the value , then the second operand is not evaluated

string

a sequence of characters usually enclosed by some syntactical delimiters ex: “ “

implementation:

• array: fixed size

• linked list: slow access to characters

mutability

when it is possible to change string length and content

arrays

simplest data structure in most imperative languages and are indexed sequence of elements on the same type

• allocated in contiguous blocks of memory

• once located, size can not be modified