1. More about Numerical Computation
Assumptions:
Graduate level
Operating Systems
Making Choices about operation systems
Why a micro-century? …just about enough time for one concept
CIS 1057 Computer Programming C
Fall 2013
(Acknowledgement: Many slides based on/borrowed from Professor Hugh C. Lauer.
Slides include materials from The C Programming Language, 2nd edition, by Kernighan and Ritchie and from C: How to Program, 5th and 6th editions, by Deitel and Deitel)
CIS 1057 Fall 2013
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2. More Numerical Operators
Relational operators
<, <=, >, >=, ==, !=
Return 0 if false, 1 if true
Let int a = 3;
Then
a < 3 returns 0 a >= 3 returns 1 a == 3 returns 1 a != 3 returns 0
CIS 1057 Fall 2013
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3. More Numerical Operators
Relational operators are not special in C. They are just like any other operators in expressions
Relational operators
<, <=, >, >=, ==, !=
Return 0 if false, 1 if true
Let int a = 3;
Then
a < 3 returns 0 a >= 3 returns 1 a == 3 returns 1 a != 3 returns 0
CIS 1057 Fall 2013
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4. Precedence of Relational Operators
Comparisons: lower than arithmetic operators
Equality-inequality: lower than comparisons
See Table 2-1, p.53
Examples
i < lim - 1 means i < (lim – 1)
X + (y >= 3) returns the value X (when y < 3) and the value X+1 (when y >= 3)
CIS 1057 Fall 2013
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5. Increment & Decrement Operators
++x, --x, x++, x--
Increments or decrements x by 1
++x – increments x, returns new value of x
x++ – increments x, returns old value of x
Used in many situations, especially for loops
--x – decrements x, returns new value of x
x-- – decrements x, returns old value of x
High precedence than *, /, %
Associates right to left
CIS 1057 Fall 2013
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6. More about Numerical Computation in C
Bitwise Operations
& – bitwise AND
| – bitwise OR (inclusive)
^ – bitwise exclusive OR
<< – left shift
Same as multiplying by 2 (i.e., fills low-order bits with zeros)
>> – right shift
Machine dependent fill on left, depends upon sign bit
~ – one’s complement
May only be applied to integral types
i.e., int, short, long, char
signed or unsigned
CIS 1057 Fall 2013
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7. Conditional Expressions
expr1 ? expr2 : expr3
Evaluate expr1.
If result is true, evaluate and return expr2
Otherwise evaluate and return expr3
Example,
z = (a < b) ? a : b
Assigns z the value of a if a < b, or b otherwise
See tricky code at end of §2.11
For use in Programming Assignment #2
CIS 1057 Fall 2013
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8. Assignment Operator (yet again)
location += expression means
Add expression to the value at location and assign the result back into the same location
Similarly for -=, *=, /=, %=, ^=. |=, <<=, >>=
E.g.,
x *= a is the same as x = x * a
y /= b is the same as y = y * b
z <<= 3 is the same as z = z << 3
Exceptions will become apparent later in the course
CIS 1057 Fall 2013
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9. More about Numerical Computation in C
Type Conversion
May be automatic or explicit
Automatic, for signed operands:–
If either is long double, convert other to long double
Else if either is double, convert other to double
Else if either is float, convert other to float
Otherwise, convert char and short to int and then if either is long, convert other to long
I.e., “promote” numerical types from lower to higher
CIS 1057 Fall 2013
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10. Type Conversion (continued)
Automatic type conversion of unsigned integer values is
Tricky and
Machine dependent
CIS 1057 Fall 2013
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11. Explicit Type Conversion
Definition – cast
A unary operator applied to an expression to explicitly force the value to a particular type
Represented as
(type) expression
High precedence, equal to unary operators
Associates right-to-left
Example
(int) sqrt(2*pi)
Converts the square root of 2π to an integer and truncates the fractional part (i.e., no rounding)
CIS 1057 Fall 2013
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12. More about Numerical Computation in C
Questions?
Read or review Chapter 2
CIS 1057 Fall 2013
More about Numerical Computation in C