Basic Types

CGS 3460, Lecture 19Feb 22, 2006Hen-I Yang

Previously… goto, null statement Road map to more advanced topics.

Agenda

Homework 3 Types int float

A Glimpse of Quiz 2 What is in Quiz 2?

Everything related to Homework2 Everything in the textbook up to Section 5-2 Everything listed on the “topics” page up to Feb 10

About Quiz 2 Bring Gator 1 ID 20 minutes starting 9:35 am sharp No electronic device of any sort is allowed To have homework 2 counted toward your grade, you

have to take quiz 2. Lecture will continue after the completion of the quiz

Homework 3: Prologue

Professor Dumbledore has just accepted to join UF as a visiting professor for one year. As the house/apartment rental season fast approaching, he is trying to find the best housing available for his family in the Gainesville area as soon as possible.

Homework 3: Problem 1 Realty Consultant Problem 3.1 Pick best house out of five

Homework 3 (II): Problem 2 Draw a Map Find

OptimalHouseLocation

Homework 3 (III) Hints How do we calculate absolute values?

A function called abs() [NOT ALLOWED] if (x > y) z = x – y; else z = y – x; z = (x > y) ? x – y : y – x;

How do we work through two dimension grids? Nested loops for (x = 1; x <=25; x++) {

for (y = 1; y <= 25; y++) { // You may need to check for special locations printf(“.”);

}printf(“\n”);

}

STAGE 3

We are moving on the more advance materials now.

Types: What are they, why are they important

Arrays: Tired of declaring 10 variables for 10 entries of the same thing?

Functions: How do we pack code segments into something more meaningful?

Pointers: Let the fun begins.

Types

Every data of variable is stored in the form of binary.

Compiler/CPU handles the variables based on what the programmer makes of it

Compiler does “type conversion” automatically based on certain rules

Programmers can explicitly make data another type that it was not meant to be (casting)

Types (II)

Three basic types int floatchar

The range and precision of value, or even presentation of the value of a variable can hold is machine dependent.

C language specification is flexible in these “details”

intint, short, longsigned, unsigned Integers are stored as binary, sometimes with bit sign You can specify different “sizes” of int You can also specify signed and unsigned flavor of int beware of the max/min of int, otherwise it might overflow

The max/min depends on whether the machine is 16 or 32 bits, also depends on signed/unsigned

By default, int are signed (unsigned has be to specifically declared)

If a 16-bit integer, with maximum allowed value 32767 is barely enough, then use long int

Long/unsigned/int can be permuted (order does not matter, int can be omitted)

Int (II) The values are machine dependent However, the relative size of short, int and long always r

emain Rangeshort <= Rangeint <= Rangelong Usually, if an integer is expected to exceed 32767, we us

e long for portability, but long may operate more slowly because there are more bits to operate on

Revisit: Decimal, Octal 017 0377, Hexadecimal 0xf 0xff 0xFF 0XFF

When specified as a constant expression 15L, 0377L, 0x7fffL (long) 15U, 0377U, 0x7fffU (unsigned)

More conversion specifications %u, %o, %x, %hd (short), %ld (long) %d only work for int

Summary

Quiz 2 Homework 3 Type int

Before you go

Read Chapter 7. Exercise: 7.3, 7.4 Quiz 2 on Feb 24, Friday at 9:35 am,

remember to bring Gator 1 ID card Homework 2 late submission ends

tomorrow night (Feb 23, Thursday at 11:59 pm)