1. 16.216 ECE Application Programming
Instructor: Dr. Michael Geiger
Fall 2011
Lecture 2: Basic C program structure
Number system basics

2. ECE Application Programming: Lecture 2
Lecture outline
Announcements/reminders
Course home page:
Need for discussion group (to be set up)
Office hours change:
No T 11-1
Adding Th 11-1
Will be on campus M/T—just don’t have formal office hours
Assignment 1 available today, due Friday
Assignment 2 coming Friday, due 9/16
IDE updates (see next slide)
Today
Basic C program structure
Preprocessor directives
Main program
Simple output
Representing data in C: number systems
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ECE Application Programming: Lecture 2

3. ECE Application Programming: Lecture 2
IDE updates
Any IDE that allows you to write C programs is acceptable, but you only need one
Mac users: Xcode is free
Eclipse
Can be installed on any platform
A couple of potentially useful links (install/use for Linux/Windows)
library/os-ecc/
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ECE Application Programming: Lecture 2

4. ECE Application Programming: Lecture 2
Our first C program
#include <stdio.h> int main() { printf("Hello World!\n"); return 0; }
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ECE Application Programming: Lecture 2

5. ECE Application Programming: Lecture 2
Our first C program
# indicates pre-processor directive
include is the directive
stdio.h is the name of the file to "insert" into our program. The <> means it is part of the C development system
#include <stdio.h> int main() { printf("Hello World!\n"); return 0; }
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ECE Application Programming: Lecture 2

6. ECE Application Programming: Lecture 2
Our first C program
main is the name of the primary (or main) procedure. All ANSI C programs must have a main routine named main
The () indicates that main is the name of a procedure. All procedure references must be followed with ()
#include <stdio.h> int main() { printf("Hello World!\n"); return 0; }
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ECE Application Programming: Lecture 2

7. ECE Application Programming: Lecture 2
Our first C program
{ } enclose a "block". A block is zero or more C statements. Note that code inside a block is typically indented for readability—knowing what code is inside the current block is quite useful.
#include <stdio.h> int main() { printf("Hello World!\n"); return 0; }
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ECE Application Programming: Lecture 2

8. ECE Application Programming: Lecture 2
Our first C program
printf() is a "built-in" function (which is actually defined in stdio.h).
"Hello World!" is the string to print. More formally, this is called the control string or control specifier.
#include <stdio.h> int main() { printf("Hello World!\n"); return 0; }
Every statement must end with a ";". Preprocessing directives do not end with a ";" (but must end with a return).
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ECE Application Programming: Lecture 2

9. ECE Application Programming: Lecture 2
Our first C program
The \n is an escape character used by the printf function; inserting this character in the control string causes a “newline” to be printed—it’s as if you hit the “Enter” key
#include <stdio.h> int main() { printf("Hello World!\n"); return 0; }
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ECE Application Programming: Lecture 2

10. ECE Application Programming: Lecture 2
Our first C program
The int tells the compiler our main() program will return an integer to the operating system; the return tells what integer value to return. This keyword could be void, indicating that the program returns nothing to the OS.
#include <stdio.h> int main() { printf("Hello World!\n"); return 0; }
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ECE Application Programming: Lecture 2

11. Variations #1 of first program
#include <stdio.h> int main() { printf("Hello"); printf("there"); printf("World!"); return 0; }
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ECE Application Programming: Lecture 2

12. Variations #2 of first program
#include <stdio.h> int main() { printf("Hello\n"); printf("there\n"); printf("World!\n"); return 0; }
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ECE Application Programming: Lecture 2

13. Variations #3 of first program
#include <stdio.h> int main() { printf("Hello\nthere\nWorld!\n"); return 0; }
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ECE Application Programming: Lecture 2

14. Variations #4 of first program
#include <stdio.h> int main(){printf ("Hello\nthere\nWorld!\n");return 0;}
Note while this is syntactically correct, it leaves much to be desired in terms of readability.
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ECE Application Programming: Lecture 2

15. ECE Application Programming: Lecture 2
Code readability
Readability wouldn’t matter if:
Entire code project written by one person
All code was in same file
Same person is the only one to use the code
Code was used only for a short period of time
More typically:
Projects are split—multiple programmers and files
Code usually reused
Multiple users
Used/adapted (hopefully) over long period of time
You may reuse code ... but forget what you originally wrote!
Bottom line: code needs to be readable
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ECE Application Programming: Lecture 2

16. ECE Application Programming: Lecture 2
Comments
C allows you to add comments to your code
Single line comments: start with //
Multi-line comments: start with /*
end with */
Typical uses
Multi-line comment at start of program with
Author’s name (& other info if appropriate)
Date started/modified
File name
Description of overall file functionality
For individual code sections
Single/multi-line comment for major section of code performing single function
Single line comment for single line of code if that line alone is important
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ECE Application Programming: Lecture 2

17. ECE Application Programming: Lecture 2
Comment example
/* * ECE Application Programming * Instructor: M. Geiger * 5/17/2018 * hello.cpp: Intro program to demonstrate * basic C program structure and output */ #include <stdio.h> // Standard I/O library /* Main program: prints basic string and exits */ int main() { printf("Hello World!\n"); return 0; }
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ECE Application Programming: Lecture 2

18. Number representation: bases
Humans operate in decimal (base 10)
Why don’t computers?
Computers operate in binary (base 2)
Each digit is a bit (binary digit)
Can also use octal (base 8) or hexadecimal (base 16)
Hex digits: 0-15, with A = 10, B = 11, C = 12, D = 13, E = 14, F = 15
Base conversion
Binary  hex: start with LSB and make 4-bit groups
e.g = 1B716 = 0x1B7
Note that an extra 0 is implied for the first group: 0010001
Binary  decimal: multiply bit 0 by 20, bit 1 by 21, etc.
e.g = (0 x 23) + (1 x 22) + (1 x 21) + (1 x 20) =
= = 710
Decimal  binary / hex: repeated integer division, where remainder gives you each digit, starting with LSB
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CIS 273: Lecture 9

19. Decimal  binary / hex example
3510 = ?2
35 / 2 = 17 R1 (LSB)
17 / 2 = 8 R1
8 / 2 = 4 R0
4 / 2 = 2 R0
2 / 2 = 1 R0
1 / 2 = 0 R1 (MSB)
 3510 =
3510 = ?16
35 / 16 = 2 R3 (LS digit)
2 / 16 = 0 R2 (MS digit)
 3510 = 2316
Double-check: does this answer match the binary value we found?
 2316
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CIS 273: Lecture 9

20. Base Conversions
Convert 2BAD|16 to Base 10 2 B A D |16 = ? |10 | | | | | | | `--- D x 160 = 13 x 1 = 13 | | `----- A x 161 = 10 x 16 = 160 | ` B x 162 = 11 x 256 = 2816 ` x 163 = 2 x 4096 = Therefore, 2BAD|16 = 11181|10

21. Base Conversions
Convert 20DD|16 to Base 10 ??

22. Base Conversions
Convert 20DD|16 to Base D D |16 = ? |10 | | | | | | | `--- D x 160 = 13 x 1 = 13 | | `----- D x 161 = 13 x 16 = 208 | ` x 162 = 0 x 256 = 0 ` x 163 = 2 x 4096 = Therefore, 20DD|16 = 8413|10

23. Base Conversions
Convert FACE|16 to Base 10 ??

24. Base Conversions
Convert FACE|16 to Base 10 F A C E |16 = ? |10 | | | | | | | `--- E x 160 = 14 x 1 = 14 | | `----- C x 161 = 12 x 16 = 192 | ` A x 162 = 10 x 256 = 2560 ` F x 163 = 15 x 4096 = Therefore, FACE|16 = 64206|10

25. Work from right to left Divide into 4 bit groups
Base Conversions
Dec
Bin
Oct
Hex
0000 00 1
0001 01 2
0010 02 3
0011 03 4
0100 04 5
0101 05 6
0110 06 7
0111 07 8
1000 10 9
1001 11
1010 12 A
1011 13 B
1100 14 C
1101 15 D
1110 16 E
1111 17 F
|2=?|16 ##
2 B D
|2=2B8D|16
NOTE: # is a place holder for zero
Work from right to left Divide into 4 bit groups

26. Base Conversions FACE|16=?|2 F A C E 1111 1010 1100 1110
Dec
Bin
Oct
Hex
0000 00 1
0001 01 2
0010 02 3
0011 03 4
0100 04 5
0101 05 6
0110 06 7
0111 07 8
1000 10 9
1001 11
1010 12 A
1011 13 B
1100 14 C
1101 15 D
1110 16 E
1111 17 F
FACE|16=?|2
F A C E
\ FACE|16= |2

27. Example 1: Base conversions
Perform the following base conversions
1110 = ?2 = ?16
3710 = ?2 = ?16
1116 = ?10
0x2F = ?2 = ?10
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ECE Application Programming: Lecture 8

28. ECE Application Programming: Lecture 8
Example 1 solution
Perform the following base conversions
1110 = = B16
3710 = = 2516
1116 = 1710
0x2F = = 4710
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ECE Application Programming: Lecture 8

29. ECE Application Programming: Lecture 2
Visual Studio demo
Brief demonstration to show
Starting new project
Entering code
Executing basic code
Dealing with simple compiler/linker errors
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ECE Application Programming: Lecture 2

30. ECE Application Programming: Lecture 2
Assignment #1
Basic assignment to ensure you can write, run, and submit programs
Write a short program that prints (each item on its own line):
Your name
Your major
Your class (i.e. freshman, sophomore, etc.)
The name and semester of this course
Submit only your source (prog1_simple.c) file via to
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ECE Application Programming: Lecture 2

31. ECE Application Programming: Lecture 2
Next time
Using data in C
Basic I/O
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ECE Application Programming: Lecture 2