Introduction An array is a fixed-size sequenced collection of elements of the same data type. List of temperatures recorded every hour in a day, or a month, or a year. List of employees in an organization. List of products and their cost sold by a store. Test scores of a class of students. List of customers and their telephone numbers Table of daily rainfall data.
1D Arrays and Random Numbers Artem A. Lenskiy, PhD May 26, 2014
Introduction In addition to arrays and structures, C supports
creation and manipulation of the following data structures: Linked
lists Stacks Queues Trees Data Types Derived typesFundamental
typesUser-defined types Arrays Functions Pointers Integral types
Float types Character types Structures Unions Enumerations
Introduction An array is a fixed-size sequenced collection of
elements of the same data type. List of temperatures recorded every
hour in a day, or a month, or a year. List of employees in an
organization. List of products and their cost sold by a store. Test
scores of a class of students. List of customers and their
telephone numbers Table of daily rainfall data. Arrays :
Declaration An array declaration tells the compiler how many
elements the array contains and what the type is for these
elements. The number enclosed in the brackets indicates the number
of elements in the array. The numbering starts with 0. Candy[0] is
the first element. Candy[364] is the 365th and last element. type
variable-name [size] Arrays : Initialization When you use empty
brackets to initialize an array, the compiler counts the number of
items in the list and makes the array that large. sizeof days is
the size, in bytes, of the whole array, and sizeof days[0] is the
size, in bytes, of one element. Using const with Arrays The program
treat each element in the array as a constant Array can be
explicitly initialized at run time. i threshold[i] We can use
scanf() to initialize array Arrays Run-time initialization Arrays
Run-time initialization: Example Given the list of marks obtained
by a class of 50 students in an annual examination.
43,65,51,27,79,11,56,61,82,09,25,36,07,49,55,63,74,81,49,37,
40,49,16,75,87,91,33,24,58,78,65,56,76,67,45,54,36,63,12,21
73,49,51,19,39,49,68,93,85,59 Write a program to count the number
of students belonging to each of following groups of marks:
Frequency Groups 0-9, 10-19, 20-29,,90-100 Arrays Run-time
initialization: Example Run-time initialization: Example (cont)
Frequency Groups Arrays : Not initialized If an array is not
initialized, the elements might have any value. The compiler just
uses whatever values were already present at those memory locations
Arrays : Partially initialized 11 If an array is initialized
partially, the remaining elements are set to 0. Non-valid array
assignment Array Bounds int doofi[20]; It's your responsibility to
make sure the program uses indices only in the range 0 through 19,
because the compiler won't check for you. The compiler doesn't
check to see whether the indices are valid. The result of using a
bad index is, in the language of the C standard, undefined. So, the
program, might seem to work, it might work oddly, or it might abort
(Run-time error). Non-valid array assignment Correct indexes
Incorrect indexes Specifying an Array Size wrong correct wrong
Example Write a program to evaluate the following expression The
values of x 1, x 2, are read from the terminal Random numbers
generator A random number generator (RNG) is a computational or
physical device designed to generate a sequence of numbers or
symbols that lack any pattern, i.e. appear random. In C language
library provides two function to generate random numbers: rand()
return a pseudo-random integer between 0 and RAND_MAX (32767)
srand(unsigned int seed) sets seed as the seed for a new sequence
of pseudo-random integers to be return by rand(); Rand() rand()
return a pseudo-random integer between 0 and RAND_MAX (32767) First
run Second run Seed definition Observation: The results of several
runs are identical Explanation: The initial seed used by rand() is
identical each time. The seed: Used for the generation of the
random numbers. Explicitly specified using the srand function
srand() srand(unsigned int seed) sets seed as the seed for a new
sequence of pseudo-random integers to be return by rand(); The
sequences can be repeatable by calling srand() with the same seed
value. The system time is a good choice as an argument for srand().
It will be different each time the program is run. Thus, results
will also be different. rand() and srand() First run Second run
Functions rand() and srand() are defined in. You dont need to
implement them just #include. Example: Dices with rand() a[ i ] is
a histogram and counts how many times a pair of dice rolled i.
rand() % 6 produces random numbers in the range 0 to 5, rand() %
produces random numbers in the range 1 to 6. First run Second run
Example: Dices with rand() and srand() a[ i ] is a histogram and
counts how many times a pair of dice rolled i. rand() % 6 produces
random numbers in the range 0 to 5, rand() % produces random
numbers in the range 1 to 6. First run Second run Review questions
Identify errors, assuming that ROW and COLUMN are declared as
symbolic constants: What happens when an array with a specified
size is assigned With values fewer than the specified size; and
With values more than the specified size. 23
