EECE.2160 ECE Application Programming Instructors: Dr. Michael Geiger & Peilong Li Spring 2016 Lecture 2: Basic C program structure Data in C: Data types, constants, and variables

ECE Application Programming: Lecture 2 Lecture outline Announcements/reminders Sign up for the course discussion group Program 1 due Wednesday, 1/27 10 points: e-mail Dr. Geiger for shared Dropbox folder 10 points: introduce yourself to your instructor 30 points: complete simple C program Today’s lecture Basic C program structure Comments Data types Constants Visual Studio demo 4/30/2019 ECE Application Programming: Lecture 2

ECE Application Programming: Lecture 1 Our first C program #include <stdio.h> int main() { printf("Hello World!\n"); return 0; } 4/30/2019 ECE Application Programming: Lecture 1

ECE Application Programming: Lecture 1 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; } 4/30/2019 ECE Application Programming: Lecture 1

ECE Application Programming: Lecture 1 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; } 4/30/2019 ECE Application Programming: Lecture 1

ECE Application Programming: Lecture 1 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; } 4/30/2019 ECE Application Programming: Lecture 1

ECE Application Programming: Lecture 1 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). 4/30/2019 ECE Application Programming: Lecture 1

ECE Application Programming: Lecture 1 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; } 4/30/2019 ECE Application Programming: Lecture 1

ECE Application Programming: Lecture 1 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; } 4/30/2019 ECE Application Programming: Lecture 1

Variations #1 of first program #include <stdio.h> int main() { printf("Hello"); printf("there"); printf("World!"); return 0; } 4/30/2019 ECE Application Programming: Lecture 1

Variations #2 of first program #include <stdio.h> int main() { printf("Hello\n"); printf("there\n"); printf("World!\n"); return 0; } 4/30/2019 ECE Application Programming: Lecture 1

Variations #3 of first program #include <stdio.h> int main() { printf("Hello\nthere\nWorld!\n"); return 0; } 4/30/2019 ECE Application Programming: Lecture 1

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. 4/30/2019 ECE Application Programming: Lecture 1

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 4/30/2019 ECE Application Programming: Lecture 2

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 4/30/2019 ECE Application Programming: Lecture 2

ECE Application Programming: Lecture 2 Comment example /* 16.216 ECE Application Programming Instructor: M. Geiger 4/30/2019 hello.c: Intro program to demonstrate basic C program structure and output */ #include <stdio.h> // Main program: prints basic string and exits int main() { printf("Hello World!\n"); // Comment return 0; } 4/30/2019 ECE Application Programming: Lecture 2

ECE Application Programming: Lecture 2 Representing data in C Two major questions (for now) What kind of data are we trying to represent? Data types Can the program change the data? Constants vs. variables 4/30/2019 ECE Application Programming: Lecture 2

Four Types of Basic Data Integer int Floating point (single precision) float Double Precision double Character char 4/30/2019 ECE Application Programming: Lecture 2

ECE Application Programming: Lecture 2 Integer Constants Any positive or negative number without a decimal point (or other illegal symbol). Legal values: 5 -10 +25 1000 253 -26351 +98 Illegal values: 2,523 (comma) 6.5 (decimal point) $59 (dollar sign) 5. (decimal point) 4/30/2019 ECE Application Programming: Lecture 2

Range of Integers (Machine Dependent) unsigned signed char 0  255 -128  +127 (8 bits) short int 0  65535 -32768  + 32767 short (16 bits) int 0 to 4294967295 -2147483648  2147483647 long long int (32 bits) 4/30/2019 ECE Application Programming: Lecture 2

float/double Constants Any signed or unsigned number with a decimal point Legal values: 5. .6 +2.7 0.0 -6.5 +8. 43.4 Legal (exponential notation): 1.624e3 7.32e-2 6.02e23 1.0e2 -4.23e2 +4.0e2 1.23e-4 +11.2e+7 Illegal: $54.23 6,349.70 1.0E5 4/30/2019 ECE Application Programming: Lecture 2

float/double Constants Range of float (32 bits) ± 1.175494351 E – 38 ± 3.402823466 E + 38 Range of double (64 bits) ± 2.2250738585072014 E – 308 ± 1.7976931348623158 E + 308 4/30/2019 ECE Application Programming: Lecture 2

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 to your Dropbox folder File name matters! 4/30/2019 ECE Application Programming: Lecture 2

ECE Application Programming: Lecture 2 Visual Studio demo Basics of setting up project Steps covered in detail in Program 1 spec. Xcode users: steps are very similar Choose “Start New Project” when Xcode opens Project type: Under list of “OS X” choices on the left, choose “Application” Choose “Command Line Tool” from the options that appear Name your project (project name doesn’t matter) and choose a directory. Also, ensure that the type of project is set to “C” using appropriate drop-down menu Project includes simple C file named “main.c” You can edit this file to include your own code Rename this file so the name matches the program spec 4/30/2019 ECE Application Programming: Lecture 2

ECE Application Programming: Lecture 2 Final notes Next time Variables Operators Basic output with printf() Reminders: Sign up for the course discussion group Program 1 due Wednesday, 1/27 10 points: e-mail Dr. Geiger for shared Dropbox folder 10 points: introduce yourself to your instructor 30 points: complete simple C program 4/30/2019 ECE Application Programming: Lecture 2