4 – History of Programming Languages CSCI N201 Programming Concepts and Database 4 – History of Programming Languages Lingma Acheson linglu@iupui.edu Department of Computer and Information Science, IUPUI

Progression Hardware Machine code Assemblers Compilers Interpreters

Hardware encoding Physically wiring the machine Changing the hardware structure Programming in this way is - Very difficult - Extremely tedious - Error prone - Hard to fix problems

Hardware encoding Change physical structure of machine Extremely tedious Very difficult Prone to error

Machine Language Stored Language Concept Von Neumann Treat Instructions as data Each opcode built into ALU has a number Abniac http://wally.cs.iupui.edu/n100/update/AbApplet.html

Machine Language Abniac Illustrate the usage of machine languages All commands have a number Store – 1 Add – 2 Compare – 3 All cells (place holders) have a number 0 – 99, to store instructions and values Machine codes in second blue column Description in third blue column Output window in right most window frame

Machine Language Program can be created by selecting a command, enter values and click on “OK” button Need to run the program after it’s created - click on “Run”. Need to tell the program where to stop running - click on a cell and click “Halt”. “File -> New” to refresh and create a new program.

Machine Language Run Abniac! Create your own Abniac program!

ASCII table

Assembler Mnemonics for opcodes Labeled cells, e.g. cell x E.g. use “Add” to mean “add” Labeled cells, e.g. cell x somewhat easier on programmers E.g. Sto 2 Add 3 Lod 5 …

High-level Language Typed in near-human language Converted to assembler Much easier on programmers Can be assembled or compiled Language is still very precise, but more readable E.g. If (x=2) then response.write “two” else response.write “zero”