Difference between revisions of "Lecture 3" - Rhea

Revision as of 11:31, 22 January 2012

Lecture 3 – 1/17/2012

In class quiz – Know 3 or more classmates, their names, hometown, interests, career goals (submitted at the end of class)

Reminder
• Exercise 1 due this coming Friday (January 20th)
• Write Programs in EE206
• Check blackboard everyday
• Submit your signature on the class policy sheet given the first day of class
• Office Hours:
o Tuesday and Friday after class in MSEE222, open door policy. You can discuss any topic.

Today’s Programs
• Review of simple C programs
• Programming in Linux
• Maze files and rules
• Arc and argv
• Program to read characters in a file
• Function calls
• Practice how to write a program that can find 26 English characters and tell which ones appear the most often (ignore cases)
• Challenge: Write a program that can generate valid mazes

In Linux…
• mkdir → makes a new directory (folder)
o EX: mkdir ECE264
• ls → lists the files in the directory
o EX: ls
• cd → changes the directory
o EX: cd Exercises
• File → determines what type of file you are dealing with
o EX: file prog1 (returns a ‘.c’ file type)
• emacs/vi filename.c → creates a file and puts it into a text editor of choice

NOTE: Make sure never to have space in file name

• What is used to compile programs?
o   Linux:         gcc prog1.c -o prog1
o   Translation: Compiler     Human Readable   Name of Output file   Machine Readable

o   Linux: ./(no space)ex1 data
o   Translation: Run Machine Readable and use a text file called data

Example 1:

a =1
b=2
if(a>b)
printf(“…”);
a = 5

What is the value of ‘a’ here? a = 5.

• In the statement above, it doesn’t matter what is inside the if statement because ‘a’ is later redefined to be a OUTSIDE the if statement
• Always remember to use brackets with all logic statements
• No “end” in C (as in MATLAB if statements)

Indexing
• In C, index always begins with 0

int arr[6];

for( c = 0; c < 6; c++)
{
c will be 0,1,2,3,4,5
}

It is wrong to do the following:

int arr[6];

for( c = 0; c <= 6; c++)
{
c will be 0,1,2,3,4,5,6 ERROR: INDEX OUT OF RANGE
}

Inputting a string
• scanf(“%s”, str);
• printf(“%s”, str);

Maze program:
• Each wall is one layer thick
• Always one exit, one start
• Always one solution
• Pathways are on * in length

argc and argv
• Same as for function arguments,

int add( int a , int b)

• But instead,

Int main ( int argc , char *argv[] )

(# of arguments, array of each argument)

• The first argument is always the name of the command
• Several spaces count only as 1 space separating the arguments