Lecture 2 Flashcards by May Ca

GDB run does what?

Executes the program

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gdb break does what?

set a breakpoint (a place for the program to stop)

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gdb next

Run until the next instruction in this function(don’t follow function calls)

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gdb step

Stop at the next instruction call anywhere (goes into function calls)

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gdb continue

run until the next breakpoint

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gdb print

show the value of a variable

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gdb set

change the value of a variable

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gdb jump

Start executing at a different line number

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gdb enable/disable

enable or disable breakpoints

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What is the standard format of a switch?

switch(class) {
1: report 1
2: report 2
3: report 3
}

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What are the five ways to leave a loop iteration in c?

Finish the code flow in the loop
Continue-command that says to go to the next loop iteration
Break-leave the current block of code
Goto: has you redirect to a specific line of the program, identified by a label
Return: leave the current function completely

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Why are we discouraged from using goto?

To avoid ‘spaghetti code’.

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What is a useful purpose of goto?

Is to jump to error code before leaving the function

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Why do some style guides prefer having a single exit point for a loop or function?

Makes for easier debugging and understanding of when you have left the block of code

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What do functions return?

A return statement

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Do procedures also return a return statement?

Nope!

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How should you aim to keep functions?

Small and with a well defined purpose

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Can variables declared inside of a function or procedure be used outside of the function?

Nope!

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What happens to values of variables once the function is complete

They disappear

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How can you prevent variable values from disappearing once the function is complete?

Use a static variable

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What are the four parts of a running program?

Executable code of the program

Global variables

Call stack

Heap

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Which sections of the anatomy of a running program are created at compile time?

The executable code and the global variables

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What type of data structure is the call stack?

LIFO; last in first out

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When we call a function, what is created?

A stack frame

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Where is the stack frame added once a function is called?

The call stack

What does a stack frame contain?

The instructions to execute in the calling function when the function ends Hardware information that the current function will change and need to be restored for the calling function The parameters for the function Space for local variables for the function

What happens when the function ends?

The stack frame for the function is removed from the call stack, so all the information disappears.

What is always bottom of the stack?

Main local variables

What data type of a single character?

A char data type

Is a single character a byte?

Yes!

Does char hold unicode values?

no, it is treated as a byte (number

What is \n?

Carriage return

What is \r?

Line feed

What is \r used for?

Network protocols

Wat is \t?

Tab character

What is a C string?

C strings are arrays of characters

How do you identify the end of a string?

With a NULL character?

How do you assign, compare, copy or work on strings?

Using a string library to do the work

What is argc?

Argument count: the number of strings in the list of parameters

What is argv?

Argument values- the strings passed to the program

How do we manage arguments?

Main is always provided with at least one argument: the name of the program when it was invokved

How does the name of the program appear?

Always appears as argh[0]

Typical steps for a main function?

Set up default values for parameters Loop through all of arg v to store parameters updates get on with the typical work

How do you include a C string library?

#include

What does strlen do?

Return the number of characters in the string

Is strcmp safe or unsafe?

unsafe

What is the printing pattern for a double?

What is the printing value for a char?

For signed data, what bit identifies whether the data is positive or negative?

The leftmost bit

What does the const modifier do

Flag that this variables value shouldn't change after initialization Often used in parameter declarations

What does the static modifier do?

For a local variable, ask for its space to be somewhere other than the stack so the value survives across function invocations

Type coercions go in one direction? True or False

True

What does the command typedef do?

Lets you give a different name to existing commands

What are three ways to create your own data types?

- Struct - Enum - Union

Which two data type creation methods can nest within one another?

Structs and unions

Where can an enum appear?

Inside a struct or a union

What is the structure of a typedef?

typedef struct { float x; float y; } point; point p; p. x = 5 p. y = 10.5

How do you initialize a stack?

- Set the stack to have no entries - Store the size of the stack - Return whether or not the initialization is successful

How do you destroy a stack?

Reset the stack to be empty | Nothing to return..what can the user do if we don't clean up properly? nothing, so no use telling them.

How do we push to a stack?

If space remains then append to the array, move the top spot in the array. Else, report that we can't add to the stack.

How do we pop from a stack?

If there is something in the stack then remove from the end of the array, move the top spot in the array, return both success and the integer removed

When a struct is passed as a parameter to a function, a copy of the whole struct is placed where?

The call stack

What is a pass by reference?

Pass the location of the data in :main: to the functions rather than the data itself

What is a pointer?

A data type that contains a memory address

What do we use a pointer for?

To indirectly get to the values of variables

What are the two values of pointers?

An address stored by the pointer The value at the address where the pointer points

When a pointer is declared, is the space also set aside?

no, the space must be declared separately

The address stored in the pointer must assign what?

A memory address to the pointer

What are the two options for function declarations in a C file?

Include all the code for a function before it is used Define a prototype of the function at the top of the C file and then give the code later

How do you compile with multiple C files in one gcc command?

gcc -o executable file1.c file2.c file3.

How do we use a function from another file?

Put a prototype in its own file and use include 's in each c file that requires it.

How do we read in an include file?

#include "filename.h"