Class Objectives · The objectives of this class are as follows

· Teach you how to write C programs

· Teach you how to debug C programs

· Teach you how to design good C programs

· Managers are certainly invited to attend, but they must plan to do real work

· "90 percent of life is just showing up." --Woody Allen

· Exams are heavily based on material presented in class…
· Never miss more than one consecutive week of classes

· If you just have to take that two week vacation, plan it so that you only miss one week of classes -- really!

· Missing even one class will severely limit your ability to keep up, particularly wrt the exams
· Read ahead
· Do the homework

· Students with a previous programming (e.g. Pascal or C++) background should plan on spending 5-10 hours per week

· Students with a no programming background but computer literate 10-20 hours per week

· Students with a no programming background and no computer experience 20-30 hours per week...you will be spending a lot of time struggling with the tools as well as learning how to program

· The best plan of action is to do a little bit of the lab assignment work each day, particularly if you have a home computer

· The worst plan of action is to do everything the night before the homework is due

· You learn C by doing, i.e., you must write C programs, compile them, and run them

• 
  Central Processing Unit (CPU) controls the flow of instructions and data and performs the necessary manipulation of data
  
• 
  Primary storage (memory) is used to store information for immediate access by the CPU
  
• 
  Note that there are many levels of cache used in primary storage
  
• 
  Secondary storage devices (e.g., the hard drive, CD-ROM drives, tapes, etc.) provide permanent storage of large amounts of data, but are much slower than primary storage
  
• 
  Input and Output devices provided interfaces between the computer and the user
  

(CPU)

• 
  The first computers used vacuum tubes to hold data
  
• 
  Vacuum tubes have two states - ON and OFF
  
• 
  An ON state represents a 1
  
• 
  An OFF state represents a 0
  
• 
  Eight vacuum tubes strung together can represent an 8 digit string of 0s and 1s
  
• 
  Put another way, this string is an 8 digit binary (base 2) number
  

• 
  We use decimal (base 10) numbers in our daily life
  
• 
  A decimal number is a string of digits whose values are drawn from the set {0,1,2,3,4,5,6,7,8,9}
  

• 
  In general, a number system is simply a way of representing numbers
  
• 
  A number system has a base (the number of digits used in the number system)
  
• 
  C
  onsider a number in a base b number system:
  

• 
  
  The value of this number is:
  

• 
  A binary number has a base of 2 where the valid digits are 0 or 1
  
• 
  E.g., 1001 binary == 9 decimal (1*8 + 0*4 + 0*2 + 1)
  
• 
  An octal number has a base of 8 where the valid digits are 0 through 7
  
• 
  E.g., 031 octal == 25 decimal (3*8 + 1)
  
• 
  A decimal number has a base of 10 where the valid digits are 0 through 9
  
• 
  E.g., 2000 decimal == 2000 (Y2K bug ;-))
  
• 
  A hexadecimal number has a base of 16 where the valid digits are 0 through F, i.e. {0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F}
  
• 
  E.g., xABBA hex == 43962 decimal (10*4096 + 11*256 + 11*16 + 10)
  

2 ^0	1	2^11	2048 2K
2^1	2	2^12	4096 4K
2^2	4	2^13	8192 8K
2^3	8	2^14	16,384 16K
2^4	16	2^15	32,768 32K
2^5	32	2^16	65,536 64K
2^6	64	2^17	131,072 128K
2^7	128	2^18	263,144 256K
2^8	256	2^19	524,288 512K
2^9	512	2^20	1,048,576 1M
2^10	1024 1K	2^21	2,097,152 2M

1 KILO = 2^10 = 1024

1 MEG = 2^20 = 1024*1024 = 1,048,576

1 GIGA = 2^30 = 1024*1024*1024 = 1,073,741,824

• 
  T
  o evaluate a binary number, say 101101, simply add up the corresponding powers of 2:
  

• 
  A hexadecimal number is a string of hexadecimal digits
  
• 
  Digits A, B, C, D, E, F represent the numbers 10, 11, 12, 13, 14, and 15
  
• 
  Hexadecimal is popular in the computer field because it can be used to concisely represent a long string of binary digits
  
• 
  Consider a 16 digit binary number:
  

• 
  Break this up into groups of 4:
  

• 
  Convert each group of 4 into decimal:
  

• 
  Then convert each decimal number into hex:
  

• 
  And you now have the number: Baker 1 Charlie 3
  

• 
  By the same token, the HEX number 3F2C1596 represents the binary string:
  

• 
  Primary storage, also known as main memory or RAM (random access memory) is used to store information for immediate access by the Central Processing Unit (CPU)
  
• 
  Memory can be viewed as a series of memory cells with each cell having its own individual address
  
• 
  E.g., think of a bank of mailboxes at a post office
  
• 
  The information contained in a memory cell is called the contents of that cell
  
• 
  Memory cells can be used to store data, such as characters or numbers
  
• 
  Internally, of course, they are all numbers, but we can choose to interpret some numbers as characters
  
• 
  They can also be used to store program instructions
  
• 
  These are “special” numbers that are meaningful to a CPU!
  

• 
  The smallest unit of computer storage is a bit, as in binary digit
  
• 
  Most computers group bits together to form larger entities
  
• 
  E.g., 8 consecutive bits often form a byte and 32 consecutive bits often form a word
  

• 
  A word on an Intel 286 computer is 16 bits or 2 bytes
  
• 
  A word on an Intel 386, 486, and Pentium computers is 32 bits or 4 bytes
  
• 
  The next generation of Intel computers (e.g. the Merced) will use 64 bit words, i.e. 8 bytes
  
• 
  The DEC Alpha computer is currently using 64 bit words
  
• 
  Many mainframe computers, such as the Unisys A-Series, use 48 bit words
  

• 
  Memory cells in a computer are typically one byte or one word in size
  
• 
  A word is a unit of information that can be transferred to and from memory
  

• 
  A kilobyte of memory, as in 1K, is 1024 bytes of memory
  
• 
  A megabyte of memory, as in 1M, is 1024K of memory, or 2^20 bytes
  
• 
  A gigabyte of memory, as in 1G, is 1024M of memory, or 2^30 bytes
  
• 
  Note that a 32 bit word can represent 2^32 different possible values
  

• 
  Computers only do what they are told to do
  
• 
  Except in Hollywood movies, e.g., 2001, Terminator 2, the Matrix, etc. ;-)
  
• 
  In order for a computer to perform a task, it must be given a series of specific instructions in a language it can understand
  

• 
  The fundamental language of any computer is its machine language
  
• 
  This is typically sequences of zeroes and ones
  
• 
  In the very early days of computers, this was the only way one could write programs!!!
  

• 
  To relieve the suffering of these early programmers, a higher level language called assembly language was developed
  
• 
  Assembly language contains mnemonic words and symbols for the binary machine instructions
  
• 
  An assembler maps assembly language instructions into machine language instructions
  

• 
  Assembly language programming is indeed a significant improvement over machine language programming
  
• 
  However, it has the following drawbacks:
  
• 
  Machine dependent - each computer architecture has its own unique assembly language
  
• 
  Low level instructions - writing programs is very time consuming, tedious, and error-prone
  

• 
  A general trend in computing over the past 4 decades is to elevate programming from low level to higher level languages
  
• 
  I.e., high level languages are geared more toward people writing the programs rather than the computer
  
• 
  Assembly language instructions map directly to machine instructions
  
• 
  High level language instructions must be translated/compiled into machine instructions
  

• 
  High level languages are more “problem-oriented” than assembly/machine languages
  
• 
  E.g, they require little or no knowledge of the underlying computer architecture
  
• 
  Learning how to write/debug programs in high level languages is much easier and less error-prone than learning how to write/debug equivalent programs in assembler
  
• 
  E.g., high level languages required fewer statements to do the same thing as assembler
  
• 
  Programs written in high level languages can be ported much more easily to different computer architectures
  
• 
  E.g., the compiler encapsulates the machine-dependent details of the target assembly language
  

• 
  A special program called a compiler is needed to translate a program written in a high level language into assembly code (which is then transformed into native machine code by an assembler)
  
• 
  The statement written in the high level language are called source code
  
• 
  The compiler/assembler's output is called object code
  

· Widely available, particularly on personal computers and workstations

· Can be used very portably

· Standard library

· Preprocessor may be used to isolate machine dependent code

· Unlike Pascal, which has many dialects

· Native language of UNIX (tm) and Windows NT

· Terse

· Statements can be very powerful

· Some are bit level operators

· Designed to be implemented efficiently on many machines

· Modular -- functions

· Parameters are typically passed `by value’

· No nested functions

· Syntax is complicated

· Semantics of certain features are complex and error-prone

A Comparison of Programming Language Philosophy
Pascal
· Strict Parent (a “bondage and discipline” language ;-))

· Restricts programmer for his/her own good

· A white, automatic transmission automobile with lots of safety features (e.g., air bags, controls that limit speed to 55 miles per hour and prohibit leaving the lights on or locking the keys in the car)
C
· A permissive, easy going parent (a ‘lassize-faire’ language ;-))

· Assumes that the programmer knows what he/she is doing and will assume responsibility for his/her actions. (Some describe it as a “gun with which you can shoot yourself in the foot.”)

· A bright red ’65 Corvette with a big block engine, manual transmission, optional seat belt, and with fuzzy dice hanging from the rear view mirror.
C++
· A less permissive, yet open minded parent (e.g., ‘Thomas Huxtable’ ;-))

· Assumes that the programmer generally knows what he/she is doing, but provides more checking by default. (“With C++ it’s harder to shoot yourself in the foot, but when you do, you’ll blow off both of your legs” – Bjarne Stroustrup)

· A bright red 2000 Corvette with a 6 speed manual transmission, air bag, and heads up display, many on board computers

Example C Program

/* File: hello.c Description: Prints a greeting to stdout. Author: Douglas C. Schmidt */ #include int main (void) /* execution starts in main */ { printf ("Hello world.\n"); return 0; }

· All C programs must have a function in it called main

· Execution starts in function main

· C is case sensitive!

· Comments start with /* and end with */. Comments may span over many lines.

· C is a “free format” language.

• 
  In Visual Studio, do a File|New and you will see the following dialog...
  

• 
  Here, you must first select Win32 Console Application. Then press the ... button that appears to the right of the Location
  

• 
  Now choose the location. You may need to create a folder on your file system. In this case, I brought up the Windows NT explorer and created the new folder Ece11-s98. Whatever you do, you should place the project in a place such that you can easily find it later.
  

• 
  Now that you have specified a Location, i.e. a folder where you want your project created, you should see the following...
  

• 
  Now, specify the name of your project. Visual Studio will create a folder underneath the one you specified for Location by that name. This will also become the name of your executable... Finally, click on the OK button to record your selection.
  

• 
  It is very important that you do each of these initial steps in the exact order that I have described above. That is, first specify that you want a Console Application, then specify the location, then specify the project name. Do not forget any of these steps. In other words, pay attention!!!
  

• 
  As a result, you will see the following in Visual Studio
  
• 
  N
  otice that the Workspace window now has three tabs. It has a ClassView tab, a FileView tab, and an InfoView tab. Select (point the mouse to) the FileView tab.
  

• 
  After selecting the FileView tab, you should see the following. Notice what appears in the Workspace window...
  

• 
  Now we need to create a source file and include it in the project. If we do the correct sequence of steps, Visual Studio will automatically include the new file into the project.
  

• 
  Do a File|New and select Text File and then specify a File name. Do not accept the default choice, Active Server Page (or whatever happens to be the default). Do not select C/C++ Header File. Do not select C++ Source File. Select Text File. Do not forget to type in the file name, i.e. hello.c (or whatever you wish to call it), but it must end with .c !!! The file suffix tells Visual Studio what type of file this is so it knows which compiler to invoke on it. Finally, click OK to select your choice.
  

• 
  As a result of your efforts, you should see the following.
  

• 
  I usually move the windows around at this point, adjusting the sizes.
  
• 
  Type in the program.
  

• 
  If you click on the + by Hello files under Workspace, you will see a list of all of the files in your project
  
• 
  B
  uild your program by selecting the Build|Build menu option
  

• 
  Run it (Build | Execute)
  

Now let's look at the files:

Hello.dsw: this is your WORKSPACE

Hello.dsp: this is the project build file

• 
  The program we just built is HELLO.EXE under the Debug directory
  

• 
  Because it is a CONSOLE application, we can run it directly from our Windows NT command (or Windows 95 Dos) prompt.
  
• 
  When I typed hello below at the Dos prompt, Windows ran the program hello.exe. Below you can see the results of this run.