CSC362.01, Class 3: Sample Source and Target Languages

Admin:
* Homework questions?
* Run for SGA senator.  Applications due at 5:00 p.m. today.
* Cool convo Thursday.  Extra credit for attending.
* Watch Sam suffer on a panel Thursday evening.
* Extra credit: 1/2 point for each activity; capped at 3
* There are 100 points in my class

Overview:
* More on Pascal
* Goals for this week
* What is assembly?
* PAL, A pseduo-assembly language

More stuff on Pascal you should learn
* Structured types
* Looping structures
* Procedures and functions

Basic types in Pascal
* integer
* real
* Boolean
* char

Compound types in Pascal
* Enumerated
type
  weekdays = (Monday, Tuesday, Wednesday, Thursday, Friday);
* You may not reuse names in enumerated types
* Arrays
	array[lb..ub] of type
	workload = array[Monday..Friday] of integer;
	whatever = array[10..20] of char;
   samswork: workload;
   samswork[Monday] := 10;
* Records (structs; procedure-less classes)
	person = record
	  lastname: ...;
          firstname: ...;
        end;
* String is normally a synonym for "packed array of characters"

Loops:
  for VAR := INITIAL_VALUE to ENDING_VALUE do
    STATEMENT
  for VAR := INITIAL_VALUE downto ENDING_VALUE do
    STATEMENT
  for VAR := INITIAL_VALUE to ENDING_VALUE step STEPVAL do
    STATEMENT

  for even := 0 to 100 step 2 do
    STATEMENT;

  Can you use step with non-integers?  It depends on your compiler.

  while TEST do
    STATEMENT;

  repeat
    STATEMENT-list
  until TERMINATION-CONDITION

Procedures and Functions

* Different creatures
  * Functions return values
  * Procedures do not

procedure NAME(PARAMS);
  LOCAL-VARIABLES
  LOCAL-PROCEDURES
begin
  STATEMENTS;
end

parameters are all typed


function NAME(PARAMS): TYPE;
  LOCAL-VARIABLES
  LOCAL-PROCEDURES
begin
  STATEMENTS;
end

The return value for a function is the value of the function variable when
the procedure terminates

	int increment(int x) {
	  return x+1;
	}

	function increment(x: integer): integer;
	begin
	   increment := x + 1;
	end

Pascal includes wonderful creatures known as "variable parameters".
* If you change a variable parameter within a procedure, its change is reflected in the original program.

Why some people hate var parameters

Consider the following statements

	x := 5;
	y := 6;
	writeln(x);

Goal for Wednesday: Discuss intermediate language we'll use this semester

Control instructions:
  JUMP LABEL/Address
  JUMP-If-Zero REGISTER LABEL/Address
  Jump-if-less-than REG1 REG2 LABEL/Address
  Arithmetic instructions
  Stack instructions
  Call procedure
The parameters to these instructions
  * Registers
  * Constant values (and labels)
  * Memory locations

There are links on today's outline to PAL, the Pseudo-Assembly Language