Programming is the process of translating the algorithm and flowchart to a source code in
A programme is a
set of instructions that instructs the computer to perform a task and results
in an output. To get an expected output, instructions need to follow the rules
of the programming language, which the programmer is using. These rules are
called syntax.
A programmer,
writes the programme in high level language. A high level language is any
programming language that enables development of a programme in a much more user
friendly programming context. It is independent of the computer’s hardware
architecture. It focuses more, on the programming logic rather than the
underlying hardware components such as memory addressing and register
utilisation.
The translation of
the programme from high level to low level language is done by Compilers and
Interpreters, which themselves are the programmes written in low level
languages.
BASIC, C / C++ and
Java are popular examples of high level languages.
The interpreter
reads a programme line and converts each line to machine language and executes
it.
A compiler on the
other hand, translates all the instructions of high level source code written
by a programmer in a high level programming language into low level language
(binary codes) in machine language.
ERRORS
OF A PROGRAMME
–
1. Syntax Errors
- When the grammatical rules of a programming language are violated, an error that occurs is called a syntax error.
For example, in Java, every statement
must end with a “;”.
If this “;”
is omitted, it will be considered as a
syntax error.
2. Run Time Errors
- The errors that occur during the
execution (while the programme is being run) of a programme are called Run Time errors. For example, if there is an instruction, which
attempts to divide an integer by a zero, it results in a Run Time error “Division
by zero” message.
3. Logical Errors –When there is no syntax or run time error, the programme executes, but provides an unexpected output which could be due to an incorrect logic, the programme is said to have logical error. For example, a programme which should convert a temperature in Celsius to Fahrenheit gives an incorrect answer, could have suffered a logical error due to wrong formula.
TOKENS OF A PROGRAMMING LANGUAGE –
Tokens
are the smallest building block of a programme. They are the fundamental units,
using which a programme is built. Some of the tokens in a programming language
are :
(i) Keywords – int, float, char, etc.
(ii) Identifiers - Names given to different parts of a programmes. They are named by programmers while following certain rules :
(a) Starts
with an alphabet or underscore.
(b) First
character must be followed by alphabets, digits or underscore.
(c) Space
and special characters are nor allowed.
(d) Keywords cannot be the names of the identifiers.
(iii)
Literals(Variables)
– They
are constant values. The different tupes of literals are:
(a) Integer literals, e.g.
90,
(b) Decimal literals, e.g.
89.23 or 89.23f,
(c) Character literals, e.g.
‘a’,
(d) Boolean literals, e.g.
true and false,
(e)String literals, e.g. “aditi”.
iv) Punctuator – They are also called separators. For example, comma (,) and semicolon (;).
(v)
Operators –
Symbols
applied on operands and yield a
specific result.
TYPES OF
OPERATORS
–
Equal to
sign (=) is an
assignment operator which is used to assign a value to a variable. Variable
stores a value based on the data type of the variable. E.G., int x=10;
Here, variable
x is declared as an integer variable. It can store an integer number (i.e., 10)
2. Arithmatic Operators –
3. Relational Operators –
4. Logical Operator –
A variable
is a memory location that stores data/value. The type of data that it stores depends on the data type used to declare a variable. The value of the variable can
change in a program. Variables are named by programmers following the rules for
naming identifiers.
Data Types –
A data type
represents a keyword of the programming language that allocates sufficient
storage space (memory for the data)
A program is given below to compute the area of a rectangle with length =50 cm and breadth = 15 cm. The following is to be written in the “BlueJ” application which uses the programming language of Java.
// compute
the area of a rectangle//
class prg
{
void display()
{
int length =50, breadth = 15;
int area = length * breadth;
System.out.println (“Area of given rectangle
=”+area);
}//end of
method
}//end of
class
To see the
output of the program, follow the given steps :
1. After typing the program,click on ‘compile’.
2. Close the
window and right click on the file named prg;
3. Choose ‘create
object’ and a window will open up naming the program as prg 1.Click on OK.
4. A red box
will appear at the bottom of the window. Click and open it.
5. The output
of the program will be shown as :
“Area of
given rectangle =750”
{
//
Block containing any valid Java statements if the text expression is evaluated
to true.//
else
{
// Block containing any valid Java statements
if the text expression is evaluated to false.//
void display (int n)
System –out.println (n+”is a negative number”);
}
{
System.out.println(n
+ “is a negative number”);
}
else
{
System.out.println(n + “ is a zero”);
}
}//end
of display
}//end
of class
The way to view the output will remain the same except for a slight change, i.e. once the red box with the name of the class appears at the bottom of the window,we will have to:
(ii) A box will open where we can input any numerical for the variable. This is to be done at times when the value of the variable is not mentioned in the code itself.
E.g.> In the above program (prgm) if n=5, then the output will be shown as “5 is a positive number.”
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If you have any doubt, pl. let me know