The C Programming Language continued

1
Chapter 3
The C Programming Language (continued)
2
Assignment Statements
3
Assignment Statements

• Used to assign a value to a variable
• General Form
• identifier expression
• Example 1
• double sum 0 sum
• Example 2
• int x
• x5 x
• Example 3
• char ch
• ch a a

0
5
a
4
Assignment Statements

• Can have complicated expressions on the right
  side. They must be evaluated and the resulting
  value is assigned to the target variable
  (identifier) on the left of the assignment
  operator.
• Ex. simple assignment b x1 i i 1
• Others compound assignment
• x 4 same as x x4 If x
  3, after, x 7
• x y same as x x y
• x 4 (assume x 7) then
  after, x 3
• x 3 (assume x 7) then
  after x 1

5
Assignment Statements - continued

• Example 4
• int x 0, y 0, z
• z2
• x
• y
• z
• Example 5
• yz y

6
Assignment Statements - continued

• Mixed-type Assignment Statement
• When an assignment statement is executed, the
  expression is first evaluated then the result is
  assigned to the variable listed to the left of
  the assignment operator ().
• Either a type double or a type int expression
  may be assigned to a type double variable.
• Note in a mixed-mode assignment, the expression
  has a different data type from the target
  variable.
• Example
• int m 3, n 2
• double p 2.0 m
• double x, y
• x m / p n
• y m / n p
• x

3
2
2.0
1.5
1.0
7
Increment and Decrement Operators

• Increment Operator
• post increment x
• pre increment x
• Decrement Operator - -
• post decrement x- -
• pre decrement - -x

8
Abbreviated Assignment Operator

• operator example equivalent statement
• x2 xx2
• - x-2 xx-2
• xy xxy
• / x/y xx/y
• xy xxy

9
Special Statements

• Should recognize these and know how they work.
• How about a b c ? operators
  associate right to left
• Really is a (b c)
• What results? int a, b
• float x, y
• a x y b 1.5f
• How about int ioResult scanf (d, x)
• assigns an integer value to x
• also provides the number of successful
  conversions to ioResult.
• This is a side effect of scanf(). (may be
  very useful later!!)

10
Library Functions
11
Library Functions

• A primary goal of software engineering is to
  write error-free code.
• Code reuse - reusing, whenever possible, program
  fragments that have already been written and
  tested is one way to accomplish this goal. Why
  reinvent the wheel?
• C promotes reuse, as do all programming
  languages, by providing numerous library
  functions (such as sqrt) that can be invoked to
  perform complicated mathematical computations.
• A include must be used in order to have access
  to these functions.
• Some are positioned within ltstdlib.hgt, others
  are made available by using a include ltmath.hgt
  preprocessor statement in your program.

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Math Functions that are Available
fabs(x) Absolute value of x. sqrt(x) Square root
of x, where xgt0. pow(x,y) Exponentiation, xy.
Errors occur if x0 and ylt0, or if xlt0 and y
is not an integer. ceil(x) Rounds x to the
nearest integer toward ? (infinity). Example,
ceil(2.01) is equal to 3. floor(x) Rounds x to
the nearest integer toward -? (negative
infinity). Example, floor(2.01) is equal to
2. exp(x) Computes the value of
ex. log(x) Returns ln x, the natural logarithm
of x to the base e. Errors occur if
xlt0. log10(x) Returns log10x, logarithm of x to
the base 10. Errors occur if xlt0.
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Trigonometric Functions
sin(x) Computes the sine of x, where x is in
radians. cos(x) Computes the cosine of x, where
x is in radians tan(x) Computes the tangent of
x, where x is in radians. asin(x) Computes the
arcsine or inverse sine of x, where x must
be in the range -1, 1. Returns an angle in
radians in the range -?/2,?/2. acos(x) Computes
the arccosine or inverse cosine of x, where
x must be in the range -1, 1. Returns an
angle in radians in the range 0,
?. atan(x) Computes the arctangent or inverse
tangent of x. Returns an angle in radians in
the range -?/2,?/2. atan2(y,x) Computes the
arctangent or inverse tangent of the value
y/x. Returns an angle in radians in the range
-?, ?.
14
Character Functions
toupper(ch) If ch is a lowercase letter, this
function returns the corresponding uppercase
letter otherwise, it returns ch isdigit(ch) Ret
urns a non-zero value(representing true) if ch is
a decimal digit otherwise, it returns a zero
(representing false). islower(ch) Returns a
non-zero value if ch is a lowercase letter
otherwise, it returns a zero. isupper(ch) Re
turns a non-zero value if ch is an uppercase
letter otherwise, it returns a
zero. isalpha(ch) Returns a non-zero value if
ch is an uppercase letter or a lowercase
letter otherwise, it returns a
zero. isalnum(ch) Returns a non-zero value if
ch is an alphabetic character or a numeric
digit otherwise, it returns a zero.
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Sample C program (using built-in functions)

• include ltstdio.hgt
• include ltstdlib.hgt
• include ltmath.hgt
• int main(void)
• double first, second, firstSqrt, secondSqrt,
  sumSqrt
• printf("Enter the first number ")
• scanf("lf", first)
• firstSqrt sqrt(first)
• printf("The square root is .2f\n", firstSqrt)
• printf("Enter the second number ")
• scanf("lf", second)
• secondSqrt sqrt(second)
• printf("The square root is .2f\n",
  secondSqrt)
• sumSqrt sqrt(first second)

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The char type

• char stores a character variable
• We can print char with c
• A char has a single quote not a double quote.
• We can use it like so

int main() char a, b a 'x' / Set a
to the character x / printf ("a is c\n",a)
b '\n' / This really is one character/
printf (b c",b) return 0
prints b
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Another Program Demonstrating char Type
include ltstdio.hgt int main(void) char d1,
d2, d3, d4 int x scanf(dcccc, x,
d1, d2, d3, d4) printf(dcccc, x,
d1, d2, d3, d4) return (0) If the
input is What would be the output?
97 534
97 534
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Strings
ALWAYS enclosed in double quotes! A string has a
length and a size and they are not the
same. (Previews of coming distractions) But
very important!
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• A String (any characters enclosed with double
  quotes) always has
• a null character at the end of the string (the
  \0).
• This is considered a single character and marks
  the end of the string.
• Just in case you are interested (more later)
• AB123 is a string of length five its size
  however is six.
• Size always includes the null character at the
  end.