High-level Programming Language (Pascal)

Arrays

• structured data type (e.g. array and record)
• can store a collection of data items of the same type into a table-like structure but the variables of simple data type (e.g. integer, real, char , Boolean and string) can only hold a single value at a time
• each data item stored in an array is called array element
• each element can be accessed by the array name followed by a subscript (or an index) enclosed in square brackets

  for example,
  　　StudentName[3] which access the third element of the array StudentName

  Declaration of a One Dimensional Array
  
  　　var ArrayName : array [<Index>] of <Element_type>

  • <Index>
    • can be any ordinal types (char, integer, Boolean) or subrange type (2..10 or 'a' .. 'e')
    • the range of <Index> indicates the size of one dimensional array , for example
      var StudentName : array [LowerIndex .. UpperIndex] of string;
    • the array StudentName contains (UpperIndex - LowerIndex + 1) elements
  • <Element_type>
    • represents the type of each element in an array
    • for example,
    • var StudentName : array [1..10] of string ; {string array}
    • TestScore : array [1..ClassSize] of real ; {real number array}

     

Copying an Array

• Using assignment statement
  　Array1 := Array2 ;
  Possible only when the arrays involved have the same array type
  i.e. var Array1, Array2 : array [1..6] of char;
  
  
• Using for loop, copy the element one by one

　for i := 1 to SizeOfArray do
　　Array1[i] := Array2[i] ;

Initialization of Array

• Using for loop to initialize the StudentName and TestScore to null strings and zeros respectively

　for i := 1 to ClassSize do
　　begin
　　　StudentName[i] := '' ;
　　　TestScore[i] := 0
　　end;

Input Data in an Array

• Using for loop to input the names of students in the array StudentName

　for i := 1 to ClassSize do
　　begin
　　　write ('Please enter the name : ');
　　　readln (StudentName[i])
　　end;

Declaration of a Two Dimensional Array

　　var ArrayName : array [<Row_Index>, <Col_Index>] of <Element_type>

• <Row_Index> and <Col_Index>
  • can be any ordinal types (char, integer, Boolean) or subrange type (2..10 or 'a' .. 'e')
  • the product of the range of <Row_Index> and <Col_Index> indicates the size of two dimensional array , for example

  
  　var StudentActivity : array [1 .. 40, 1..3] of string;
  
  the array StudentActivity contains (40 - 1 + 1) ’ (3 - 1 + 1) = 120 elements

• <Element_type>
  • represents the type of each element in an array
  • for example,

    
    　var StudentName : array ['A'..'E', 1..40] of string ; {string array}
    　　　TestScore : array ['A'..'E', 1..40] of real ; {real number array}

Using nested for loop to initialize, copy, input and output two dimensional array

for example, to initialize 5 rows × 7 columns Num_Table to zero

　for Row := 1 to 5 do
　　for Column := 1 to 7 do
　　　Num_Table [Row, Column] := 0