Programming Language Survey

Programming language

A notation for computing to a computer what we want it to do.

“Hardwired” Programs

Pre 1940s computers required you to adjust the internal wiring to perform different tasks.

Assembly language

A set of mnemonic symbols for instruction codes and memory locations.

Assembler

A program that translates the symbolic assembly language code to binary machine code.

Loader

A program that loads the machine code into computer memory.

Mnemonic symbols shortcomings

• Lacked abstraction of conventional mathematical notation

• Each type of computer hardware architecture has its own machine language instruction set and requires its own dialect of assembly language

FORTRAN (FORmula TRANslation Language)

• Developed by Backus in early 1950s

• Reflected the architecture of a particular type of machine

• Lacked the structured control statements and data structures of later high-level languages

• Supported algebraic notation and floating point numbers

ALGOL

• First language that was machine independent

• First language to receive a formal specification or definition

• Supported different numeric types and control statements

• Introduced arrays

Compiler

Translates programming language statements into machine code.

Pascal

Language for teaching programming in the 1970s

Ada

Language for embedded applications of U.S. Dept. of Defense

Lambda Calculus

Computational model developed by mathematician Alonzo Church which is based on the theory of recursive functions

Lisp

Programming language that uses the functional model of computation

Data abstractions

Simplify the behavior and attributes of data for humans

Ex. numbers, character strings, search trees

Control abstractions

Simplify properties of the transfer of control

Ex. loops, conditional statements, procedure calls

Basic abstractions

collect the most localized machine information

Structured abstractions

Collect intermediate information about the structure of a program

Unit abstractions

Collect large-scale information in a program

Basic data abstraction

Hides internal representation of common data values

• Variables: hide computer memory locations

• Data types: names for kinds of data values

• Declaration: process of giving a variable a name and data type

Data structure

Collects related data values into a single unit

Unit abstraction

Often associated with the concept of an abstract data type

Basic control abstractions

Statements that combine a few machine instructions into an abstract statement that is easier to understand

Syntactic sugar

A mechanism that allows you to replace a complex notation with a simpler, shorthand notation

Iterator

An object associated with a collection

Procedure/subprogram/subroutine

Groups a sequence of actions into a single action that can be called or invoked from other points in the program

Does not return anything

Function

Mathematical, returns one thing

Method

The message sent to an object to make it do something

Runtime environment

The system implementation of the program

Higher-order functions

Functions that can accept other functions as arguments and return functions as values

Unit

A stand-alone collection of procedures providing logically related services to other parts of a program

von Neumann bottleneck

Requirement that a program be described as a sequence of instructions

Imperative language

Three properties

• Sequential execution of instructions

• Use of variables representing memory locations

• Use of assignment to change the values of variables

Language syntax

Similar to the grammar of a natural language

Language semantics

Meaning of a language

A language is successful if

• It achieves the goals of its designers

• It attains widespread use in an application area

• It serves as a model for other languages that are successful

Writability

The quality of a language that enables a programmer to use it to express computation clearly, correctly, concisely, and quickly

Regularity

Refers to how well the features of a language are integrated

Three concepts:

• Generality

• Orthogonal design

• Uniformity

A language designed with security in mind…

• Discourages programming errors

• Allows errors to be discovered and reported

Semantically safe

Languages that prevent a programmer from compiling or executing any statements or expressions that violate the language definition

Extensible language

A language that allows the user to add features to it

Macro

Specifies the syntax of a piece of code that expands to other standard code when compiled

Difference between imperative programming and functional programming

The concept of a variable

In math, variables always stand for actual values

In imperative programming languages, variables refer to memory locations that store values

Referential transparency

The property whereby a function’s value depends only on the values of its arguments (and nonlocal variables)

Value semantics

Semantics in which names are associated only to values, not memory locations

In functional programming, functions are…

First-class data values

They can be computed by other functions and parameters to other functions

LISP (LISt Processing)

First language that contained many of the features of modern functional languages

Tail recursive

When the recursive steps are the last steps in any function