Programming with pascal

1
Programming with pascal

• 1. Numeric Expressions
• 2. Basic Input / Output Operations
• 3. Datatypes and Expressions

2
Numeric Operators and Expressions

• Numeric oprators of standard Pascal
• (Muplication)
• / (Real division)
• DIV (Integer division)
• MOD (Integer remainder)
• (Addition)
• - (Substraction)

3
Numeric Operators

• Hierarchy of applying and evaluating arithmrtic
  operators
• ( )
  FIRST
• / DIV MOD
• - LAST

4
Numeric Expressions

• Numeric expressions A numeric expression is any
  formulae that composed from these operators,
  numeric constants and variables.
• Examples of expressions
• 5 3 2 (result 6)
• 5 3 2 (result 13)
• 5 (3 2) (result 5)

5
Numeric Operators and Expressions

• Examples of (numeric) expressions
• I ( I should be either numeric
  constant or variable)
• J
• I 2J
• 6 4 4 3 16 / 8
• 12 / (4 2)
• 12 DIV (4 2)
• 6 (4- 43 16) / 8
• 12 N1 8 DIV 3 ( N1 is supposed to be
  integer variable or constant )

6

• Hierarchy of applying and evaluating arithmrtic
  operators
• ( )
  FIRST
• / DIV MOD
• - LAST

7

Basic Input/Output Operations

• There are four predefined procedures in Pascal
  for reading and writing to and from a file
• Output write, writeln
• Input read, readln
• The predefined procedure "write" has the general
  form
• write (expression1,expression2 ...)
• Expressioni is any (numeric) expressions or any
  explicative message (as sequence of characters,
  numbers or symbols) between apostrophes.
• gt It writes the values of one or more
  expressions and any message as it is to the
  output file (which may also be the terminal).

8
Basic Input/Output Operations

• Examples

Program surface This program compute the
surface of a rectangle and display the
result Var width, length integer Var
surf integer begin width 8 Length 13
surf width , length Write(The surface is
, surf) end.
Program Power This program compute the power of
a number and display the result Var I, Rs
integer begin I 8 Rs I I
Write(Result , Rs) end.
9
Basic Input/Output Operations

• The predefined procedure "read" has the general
  form
• read (variable1,variable2, ...)
• It reads values from the input file (which may
  also be the keyboard) and assigns them to the
  supplied variables.

10

• Examples

Program surface This program compute the
surface of any rectangle and display the
result Var width, length integer Var
surf integer Begin Write(Please enter the
value of Width,width) readln(width) Write(Pl
ease enter the value of length,length)
readln(length) surf width length
Write(The surface is , surf) end.
Program Power This program compute the power of
any number and display the result Var I, Rs
integer begin Write(Please enter the value of
I, I) Readln(I) Rs I I Write(Result
, Rs) end.
11
Basic Input/Output Operations

• The predefined procedures
• writeln (expression1,expression2,...)
• and
• readln (variable1,variable2,...)
• operate like write and read. In addition they
• generate a line feed after reading or writing.
  

12
Data Type Properties

• As a data type the integer numbers consist of a
  set of
• - values ..., -2, -1, 0, 1, 2, ... - and a set
  of operations for these values, (Like addition,
  subtraction, multiplication, division,
  remainder in division , predecessor, successor,
  etc).
• Whole numbers and their operations make up the
  integer data type in Pascal.
• Generally speaking, any data type consists of a
  Set of Objects and a Class of Operations for
  these objects.

13
Data Type Properties

• Data types are divided into two classes
• - simple data types
• - structured data types
• Data Types in Pascal

Simple Structured Integer
arrays Boolean records Reals
sets Char files Pointer enumerate
14
Standard Data Types

• In Pascal there are four simple data types, the
  objects and operations of which are already
  predefined. They are also called standard data
  types. They are
• - boolean
• - integer
• - real
• - char

15
The Boolean Data Type

• It consists of the truth values
• - true (logically true)
• - false (logically false)
• There are two kinds of operations defined for
  such boolean values
• - logical operators
• - comparison operators

16
The Boolean Data Type

• Each of the following logical operators yields a
  boolean value.
• - and (logical conjunction)- or (logical
  disjunction)- not (logical negation)
• Comparison operators are
• (equal) ltgt (not
  equal)
• lt (less or equal) lt (less)
• gt (greater) gt
  (greater or equal)
• Each of them yields a boolean value. It has been
  defined that false lt true yields true.
  (falselttrue yields true truegtfalse yields false
  trueltgtfalse yields true)

17
The Integer Data Type

• It includes a subset of all the positive and
  negative numbers the size of this subset is
  implementation dependent (e.g. from -32768 to
  32767).
• Arithmetic operators for integer objects are
• (addition) - (subtraction)
  (multiplication)
• div (integer division) mod (remainder of
  integer division)
• Examples 7 div 3 yields 2 7 mod 3 yields 1
  -7 div 3 yields -2
• -7 mod 3 yields -1
• Furthermore there are comparison operators with
  the usual meanings.
• Examples 7 lt13 yields true
• 7 gt 13 yields true
• -7 ltgt 7 yields true

18
The Integer Data Type

• The following standard functions are predefined
  for integer objects
• sqr ( I ) square of I
• abs ( I ) absolute value of I
• succ ( I ) successor of I, i.e. succ ( I ) I
  1
• pred ( I ) predecessor of I, i.e. pred ( I )
  I - 1
• odd ( I ) if I odd, then yields a boolean
  value true, otherwise yelds a boolean value
  false.
• Examples
• sqr(3) yields 9 abs(3)
  yields 3
• abs(-3) yields 3 succ(3) yields
  4
• pred(3) yields 2 odd(5) yields
  true
• odd(10) yields false

19
The Real Data Type

• Real stands for a subset of the real numbers.
• Real values can be represented in two different
  ways in Pascal
• the so-called fixed point notation
• (e.g. 13.275, 0.01 - "." is the decimal point)
• - the so-called floating point notation (e.g.
  1.3275e1, 10.0e-3 - "e" stands for the exponent
  of base 10.)
• Samples of valid real constants
• 5.0, 1.123, 47e1, 4433e-2 99.43e-21

20
The Real Data Type

• The arithmetic operators for the real data type
  are
• (addition) - (subtraction)
  (multiplication)
• / (division)
• Examples
• 2.7-5.4 yields -2.7
• 2.70.54e1 yields 8.1
• 30.0/8.0 yields 3.75
• Attention! The division operator for real numbers
  is / , that for integers is div.

21
The Real Data Type

• The comparison operators have their usual
  meanings.
• Examples
• 2.5e7 gt 2.5e6 yields true
• 2500.0 2.5e3 yields true
• The following predefined standard functions have
  their usual mathematical meanings
• sqr (square) abs (absolute value)
• sqrt (square root) exp (exponential
  function)
• In (natural logarithm) sin (sine)
• cos (cosine) arctan (arc tangent)

22
The Real Data Type

• Examples
• sqrt(0.16) 0.4
• exp(1.0) 2.71828
• With the next two standard functions real values
  can be converted to integer values
• - round(R) R is rounded to the nearest
  integer value
• - trunc(R) truncates the decimal fraction of
  R.
• Examples
• round(21.32) 21
• round(3.5) 4
• round(-3.5) -4
• trunc(21.32) 21
• trunc(3.5) 3

23
The Char Data Type

• This includes the set of all available
  characters. A value of type char is represented
  as a character enclosed in apostrophes.
• Example 'A', '', '3
• Please note, the char value ' 3 ' and the
  integer value 3 are not the same !
• 3 is an integer '3' is a printable character
  
• The only operators defined for char are the
  comparison operators.
• They yield results according to the alphabetical
  order.
• Examples
• 'B'lt'C yields true 'y'gt'z
  yields false
• '6'lt'7 yields true

24
The Real Data Type

• Standard functions for the char data type
• Printable characters are coded as integers in the
  computer. The most usual code for this is the
  ASCII character set, which will be used in the
  examples as well.
• - ord(C) yields the code (i.e. integer value)
  of C.
• - The inverse function of ord is chr(I) which
  maps an integer to the corresponding character.
  
• - succ(C) yields the successor of C
• - pred(C) yields the predecessor of C
• Examples
• ord('C) yields 81 ord('R') yields
  82 succ('Q) yields 'R
• chr(81) yields 'Q chr(82) yields 'R
  pred('R') yields 'Q'