CSE 1320

Donna French Formatting Based on indention and alignment

• Code blocks should be indented at least 3 spaces and not more than 5 spaces
• If tabs are used, always use tabs and set tab size to be 3-5 spaces
• If spaces are used, always use spaces and always use the same number of them
• (so basically use spaces)
• Curly braces should align vertically and be on their own line
  • Int main()
  • {
  • }
• Code formatting can make it readable, can see nested structures easily
• Less reliance on editor to match up braces and code blocks
• Makes easy grading

OLQ1

This one can only be taken multiple times OLQ2 -> 13 Are only final submission

• Need to use preformatted font when writing code in canvas for quizzes -5pts for not doing so

Tools needed for this class:

• Whatever u want
• Virtual machine works
• Visual studio code is what the class is using (can install ubuntu’s terminal in vs code)
• Slide show soon to come

Windows was based on dos Ubuntu mr popular

UNIX

• ls -> list
• ls -a -> lists hidden files, have a . in front ex. .vscode
• ls -l -> command lists more information about the files, The long description
• Touch - makes a new empty file
• mkdir -> command is used to make sub directories in home directory
• cd -> change directory, also returns to home dir
• cd .. -> takes you back a folder
• cd . -> does nothing
• cd - -> undos the previous cd
• pwd -> print working directory, tells you where you are, your file path
• cp -> copies files
• mv -> renames file, or moves it to a new name
• rm -> removes a file, deletes it
• rmdir -> deletes an empty folder
• cat filename -> entire files to the screen at once
• more filename -> displays page by page
• clear -> clears screen
• apropos a word -> displays any command that references
• man -> manual
• grep -> searches a file for a particular pattern of characters Lots of options, but basic grep is what we need to know
• diff -> displays differences in files, compares line by line, if 2 files are identical, it shows nothin

Tips & shortcuts

• history -> shows every command you have typed, can redo any of commands
• TAB completion
• Up arrow -> shows history aswell, for previous command

Computer languages can be

• High level -
  • easier for human to write, takes more for the compilers to take to machine code C++, java, easier to port between systems too
• Intermediate level
  • C is inbetween, intermediate to high level language because it allows programmers to have some control over the hardware. Assembly code can be written into a C program.
• Low level -
  • harder for human to write, more work for us, takes less for compilers to make machine code, Assembly language - used to write operating systems

Character set

ASCII

• Capped letter grouped together and small letters are too

• Used on all pc’s

• Each character has an int value between 0 and 127

• The ASCII values are used when determining the order of strings

• Need to memorize

  • A = 65
  • a = 97
  • 0 = 48
  • space = 32
  • 97 - 65 = 32
  • a - A = ( )

• Extended binary coded decimal interchange code EBCDIC

  • Used on IBM mainframes
  • Letters grouped 9 at a time
  • Stems from punch card origins and is quite difficult for programmers to deal with
  • Unicode is a expansion of ASCII

Format of C programs

(python and cobol are not free format)

• C is a free-format language
  • No requirements that code begin in a colum
  • Doesnt need multiple lines
  • Doesnt care about white spaces

Libraries in C

• A library in C is a collection of functions and definitions without a main() function
• C contains many standard libraries
  • Stdio.h
  • Math.h
  • String.h
• Can put #include anywhere, but C processes top down

Escape characters

• \n -> new line
• \t -> tab character
• \b -> backspace (doesn’t destroy what you’re backspacing over)
  • Manipulates cursor
• \” -> prints “
• \ \ -> prints \
• \0 -> null
• \007 -> audible bell
  • Need to use octal value of ascii to print
• ! -> can repeat commands that you last used

Unary

• ++M Binary
• 4+3 Ternary
• ?:

Int divisions dont give remainders If u do float divisions then you do get remainders

To get the remainder just use mod %

++ --

Arithmetic operators

High precedence

• Unary operators ++,--
• Multiplicative operators
• Additive operators
• Assignment operators

Low precedence

• Within each group the operations associate from left ot right.

() = your best friend for this

Structure programming in C

• How you “should” write your code
• Write source code that is
  • Modular
  • Easily modifiable
  • Robust (handles errors gracefully)
  • Readable
• Write functions that can be used with little or no modification in many programs
• Write functions to do one task that is not too long and can be understood easily

#include <stdio.h> is preprocesser instruction

Preprocessor

• Executes before program is compiled
• Inclusion of other files
• Start with #
• Preprocessor combines it with your program
• -E only run preprocessor, not the compiler
• Two forms of includes
• <>
  • Look in system files
• “”
  • Look in personal files
• #include
  • Go get my file and mash it together
• #define
  • Creates symbolic constants, once you set it, you cant change it
  • #define identifier replacement-text
  • #define row 4
  • No = sign
  • Adds readability
  • Easy to modify
  • UPPER CASE
  • Makes ur life easier

Expression vs statements

• Expressions
  • Sequences of tokens that can be evaluated to a numerical quantity
  • Can be number
  • Variable can be any operator in c
  • Arguments to functions
  • Somethin u can print or assign to variable
• Statements
  • May not have values
  • Purpose might be to select which statements
  • Cause sequences to happen
  • if for while

Lvalue vs rvalue expressions

• Lvalue
  • Left value
  • Location in memory such as a name of variable
  • Variables here only
• Rvalue
  • Something that can be evaluated
  • On right side
  • Variables and single numbers or operations
  • Fully evaluated then assigned to Lvalue Block statement
• A set of statements contained in braces {}
• Dont declare variables in blocks
• Curly braces are like a prison for variables

Rules of variables

• Must be declared
• Must be assigned a type
• Compiler reserves spaces in memory - amount depends on type
• Scalar types
  • Enumerated
  • Pointer
  • Arithmetic
• Aggregate types
• Function types
• Union types
• Void type
  • Doesnt return value

Int

• Scalar type
• Usually equivalent to a word
• Handled more efficiently han other types in c
• Issues
  • The size of a word varies with different hardware
    • 16bits on one computers and 32 bits on another
  • Creates portability problem
  • Largest value can vary
• Int types
  • Short int: referred as short
  • Long int: called long
  • Different sizing
• Converion specifications
  • %ld longs
  • %hd short

sizeof() vs strlen()

sizeof()-1 vs sizeof(__ . -1)

• Gives you number of bytes associated with a specified type or variable
  • Type name
  • Variable
  • Expression
• sizeof(variable-1) does nothin
  • Need to have it like sizeof(variable)-1

Overflow

• When an arithmetic operation attempts to create a numeric value that is outside of the range that cna be represented with a given number of bits we get
• Doesnt go anywhere but changes your valuable

Unsigned types

• Unsigned type gives you the whole space for positive values
• Normal types are called signed types which have negative and positive values limited to their byte size
  • Doesnt change the size of the type
• %hu unsigned short in decimal
• %u unsigned int in decimal
• %lu unsigned long in decimal

Limits.h

• Defines in min and in max
• Uint max is doubled then the normal max for a signed

Printf()- field width specifier

• Optional
• A decimal integer constant (no negatives)
• Outputs the right justfies and blanks will be used to pad on the left
• Basically css shit in c

Floating point types

• Float - single precision
• Double - double precision
• Long double - extra precision
  • Put L at thend of what it is = to
• Float.h has limits of floating point
  • You can use float.h for max of float, double and long double
• Using operators with floating points
  • Floating point + floating point = floating point
  • With a relational operator the result will be equal to an Floating point >= floating point = int (true false)
  • Float && float = int (true false) Printf () - precision specification
• Optional
• .5 tells how many numbers to print after the decimal
• Default is .6 without precision
• %f.2 ~ 1.21
  • %e gives you scientific notation

Translation of floats into binary is not perfect

• Floats do not have precise storage in computers