1. ASST. Prof. Dr. Hacer Yalım Keleş
COM101B Lecture 1: BASICS
ASST. Prof. Dr. Hacer Yalım Keleş
Reference: “Programming in ANSI C”, Kumar & Agrawal, West Publishing Co., 1992

2. The sequentıal structure
Entry -> Statement 1 -> Statement 2 -> ... -> Statement N -> Exit
Example Program:
#include <stdio.h>
int main() {
printf(«Knowledge is power\n»);
return 0; }
Reference: “Programming in ANSI C”, Kumar & Agrawal, West Publishing Co., 1992

3. CHARACTER SET
The set of characters that may appear in legal C programs is called the «character set» for a language.
This may include graphic and non-graphic characters
Graphic characters: that may be printed
Non-graphic characters: represented by escape sequences, i.e. \n, \t, etc.
There is also a null character: \0
Reference: “Programming in ANSI C”, Kumar & Agrawal, West Publishing Co., 1992

4. Reference: “Programming in ANSI C”, Kumar & Agrawal, West Publishing Co., 1992

5. C compiler groups characters into tokens:
The graphic characters, other than decimal digits, letters and blank are called special characters
Blank, horizontal and vertical tabs, newlines and formfeeds are called whitespace characters
C compiler groups characters into tokens:
A token is a sequence of one or more characters that have a uniform meaning
Some tokens are one char long, i.e. /,*,+,> etc.
Some tokens are sevaral char long, i.e. ==, >=, comments, variable names etc.
When collecting characters into tokens, the compiler always performs the longest possible tokens.
Reference: “Programming in ANSI C”, Kumar & Agrawal, West Publishing Co., 1992

6. C is a free-format language:
tokens can go anywhere on a page
Tokens can be separated by any number of whitespaces.
The program below:
int main() {
printf(«Hello»); }
Is equivalent to:
int main(){printf(«Hello»); }
Reference: “Programming in ANSI C”, Kumar & Agrawal, West Publishing Co., 1992

7. Data types Data is differentiated into types: Built-in data types:
The type of a data element restricts the set of values that the data element can take.
Built-in data types:
char: a character in the C character set
int: an integer
float: a single-precision floating point number
double: a double-precision floating point number
Some extensions: short int, long int, long double
Reference: “Programming in ANSI C”, Kumar & Agrawal, West Publishing Co., 1992

8. The qualifiers signed and unsigned can be applied to:
char, short int, int, or long int.
unsigned variables: can only have non-negative values.
signed variables: can have both positive and negative values.
In the absence of explicit usigned specification; int, long int, or short int are considered as signed.
Reference: “Programming in ANSI C”, Kumar & Agrawal, West Publishing Co., 1992

9. SIGNED REPRESENTATIONS
Ones’ Complement Representation (8 bits):
Binary value Ones’ Complement Interp. Unsigned Interpret.
Reference: “Programming in ANSI C”, Kumar & Agrawal, West Publishing Co., 1992

10. SIGNED REPRESENTATIONS
Two’s Complement Representation (8 bits):
Binary value Two’s Complement Interp. Unsigned Interpret.
Reference: “Programming in ANSI C”, Kumar & Agrawal, West Publishing Co., 1992

11. The widths of the datatypes are not specified by the C language, yet many implementations represent
a char in 8 bits,
a short in 16 bits,
an int in 16 or 32 bits,
a long in 32 bits
C specifies that:
the range of int may not be smaller than short,
the range of long may not be smaller than int,
the long double is at least as precise as a double
a double at least as precise as a float
The particular bit widths of an implementation are specified in: <limits.h> and <float.h> header files.
Reference: “Programming in ANSI C”, Kumar & Agrawal, West Publishing Co., 1992

12. Types cntd. Integral types: Floating-point types: Arithmetic types:
all types of integers and characters
Floating-point types:
float, double, long double
Arithmetic types:
Integral and floating point types
Reference: “Programming in ANSI C”, Kumar & Agrawal, West Publishing Co., 1992