Computer Programming – Grammar – data types – Variables – Keywords – Operators – decision making – Loops – Arrays – Functions – files Programming Environment

Computation model It is a formal system which defines a programming language. It also defines how the statements and expressions in a program get executed.

Declarative Computation Model Practical Programming Languages : Grammar – Extended Backus-Naur-FORM (EBNF) – Ambiguous Grammar :

? * + [ ] { }

The rules to define an integer can be written as, I  [S] D {D} | X S  +|- D  1|2|3|4|5|6|7|8|9 Z  0 With these productions, the following integers can be generated. 0, + 1, – 12, + 58, 902,

Consider the if statement in C, the production using BNF would be, I  I(C) S|I (C) S ES

It can be simplified when converted to EBNF as, I  ICS [ES]

S  a SBC | aBC CB  BC bC  bc aB  ab cC  cc bB  bb

E  E + E| E*E | a

Language Semantics : Language Design : Translation Approaches to Semantics : Data Structure of Declarative Model : – single-assignment store schema Declarative Variables : Data flow Variables

int x, y; y = 10; y = y + x;

Stateful computation model Implicit or declarative state Explicit state: Stateful collections – indexed and unindexed collections

void disp(char *str) { int k; if(strlen(str)==0) return; k=strlen(str); printf(“%c”,str[k-1]); str[k-1]=’\0’; disp(str); }

Object oriented programming model

Concurrent model. Declarative concurrent model Message passing concurrent model Lazy concurrent model

Relational model

Functional Programming model

Logic Programming model predicates fact(N,F):- fact1(N,1,F). fact1(0,F,F). fact1(N,X,F):- M is N-1, Y is X*N, fact1(M,Y,F).

Component Based Model

Graphical User Interface Programming

Distributed computation model

Constraint Programming model

Compiler ● Lexical analysis ● Syntax analysis ● Semantic analysis ● Intermediate (machine-independent) code generation ● Intermediate code optimization ● Target (machine-dependent) code generation ● Target code optimization

int main ( ) { int a, b ; float c ; a = 5 ; b = 10 ; c = a + b ; printf (“ % d”, c) ; }

LEX : Lex is a program generator

YACC YACC is parser generator

operators \ [ ]   – ?. * + \ ( ) / { } % ^

Lex keywords ● yytext ● yyleng

input ( ) –Returns the next input character. output (x) – Writes the character x on the output. unput (x) –Pushes the character x back yywrp ( )–Function called by lex when the input ends.

Structure