[SPCA] Continue summary

semester3/spca/code-examples/00_c/00_basics/02_declarations.c

@@ -1,6 +1,7 @@
 int my_int;              // Allocates memory on the stack.
                          // Variable is global (read / writable by entire program)
 static int my_local_int; // only available locally (in this file)
+extern const char *var;  // Defined in some other file
 const int MY_CONST = 10; // constant (immutable), convention: SCREAM_CASE
 
 enum { ONE, TWO } num; // Enum. ONE will get value 0, TWO has value 1

semester3/spca/code-examples/00_c/01_preprocessor/00_macros.c

@@ -0,0 +1,28 @@
+#include <stdio.h>
+#include <stdlib.h>
+#define FOO      BAZ
+#define BAR( x ) ( x + 3 )
+#define SKIP_SPACES( p )                                        \
+    do {                                                        \
+        while ( p > 0 ) { p--; }                                \
+    } while ( 0 )
+#define COMMAND( c ) { #c, c##_command } // Produces { "<val(c)>", "<val(c)>_command" }
+
+#ifdef FOO // If macro is defined, ifndef for if not defined
+    #define COURSE "SPCA"
+#else
+    #define COURSE "Systems Programming and Computer Architecture"
+#endif
+
+#if 1
+    #define OUT HELLO // if statement
+#endif
+
+int main( int argc, char *argv[] ) {
+    int i = 10;
+    SKIP_SPACES( i );
+
+    printf( "%s", COURSE );
+
+    return EXIT_SUCCESS;
+}

semester3/spca/parts/00_c/01_basics/00_intro.tex

@@ -1,7 +1,7 @@
 \subsection{Basics}
 \texttt{C} uses a very similar syntax as many other programming languages, like \texttt{Java}, \texttt{JavaScript} and many more\dots
 to be precise, it is \textit{them} that use the \texttt{C} syntax, not the other way around. So:
-\inputcodewithfilename{c}{code-examples/00_c/}{00_intro.c}
+\inputcodewithfilename{c}{code-examples/00_c/00_basics/}{00_intro.c}
 
 In \texttt{C} we are referring to the implementation of a function as a \bi{(function) definition} (correspondingly, \textit{variable definition}, if the variable is initialized)
 and to the definition of the function signature (or variables, without initializing them) as the \bi{(function) declaration} (or, correspondingly, \textit{variable declaration}).
@@ -9,4 +9,4 @@ and to the definition of the function signature (or variables, without initializ
 \texttt{C} code is usuallt split into the source files, ending in \texttt{.c} (where the local functions and variables are declared, as well as all function definitions)
 and the header files, ending in \texttt{.h}, usually sharing the filename of the source file, where the external declarations are defined.
 By convention, no definition of functions are in the \texttt{.h} files, and neither variables, but there is nothing preventing you from putting them there.
-\inputcodewithfilename{c}{code-examples/00_c/}{01_func.h}
+\inputcodewithfilename{c}{code-examples/00_c/00_basics/}{01_func.h}

semester3/spca/parts/00_c/01_basics/01_control-flow.tex

@@ -9,6 +9,6 @@ And because the labels are (as in Assembly) simply skipped over during execution
 We can also use \texttt{continue} and \texttt{break} statements similarly to \texttt{Java}, they do not however accept labels.
 (Reminder: \texttt{continue} skips the loop body and goes to the next iteration)
 
-\inputcodewithfilename{c}{code-examples/00_c/}{01_func.c}
+\inputcodewithfilename{c}{code-examples/00_c/00_basics/}{01_func.c}
 
 

semester3/spca/parts/00_c/01_basics/02_declarations.tex

@@ -2,7 +2,7 @@
 \subsubsection{Declarations}
 We have already seen a few examples for how \texttt{C} handles declarations.
 In concept they are similar (and scoping works the same) to most other \texttt{C}-like programming languages, including \texttt{Java}.
-\inputcodewithfilename{c}{code-examples/00_c/}{02_declarations.c}
+\inputcodewithfilename{c}{code-examples/00_c/00_basics/}{02_declarations.c}
 
 A peculiarity of \texttt{C} is that the bit-count is not defined by the language, but rather the hardware it is compiled for.
 \begin{fullTable}{llll}{\texttt{C} data type & typical 32-bit & ia32  & x86-64}{Comparison of byte-sizes for each datatype on different architectures}
@@ -35,3 +35,5 @@ Some will force a change of bit representation, but most won't (notably, when ca
 Another important feature is that every \lC\ statement is also an expression, see above code block for example.
 
 The \texttt{void} type has \bi{no} value and is used for untyped pointers and declaring functions with no return value
+
+It is also possible to define a custom type using \texttt{typedef <type it represents> <name of the new type>}

semester3/spca/parts/00_c/01_basics/03_operators.tex

@@ -41,3 +41,5 @@ As previously touched on, every statement is also an expression, i.e. the follow
 \mint{c}|printf("%s", x = foo(y)); // prints output of foo(y) and x has that value|
 
 Pre-increment (\texttt{++i}, new value returned) and post-increment (\texttt{i++}, old value returned) are also supported by \lC.
+
+\lC\ has an \texttt{assert} statement, but do not use it for error handling. The basic syntax is \texttt{assert( expr );}

semester3/spca/parts/00_c/01_basics/04_arrays.tex

@@ -4,4 +4,4 @@
 Unlike some other programming languages, arrays are \bi{not} dynamic length.
 
 The below snippet includes already some pointer arithmetic tricks. The variable \texttt{data} is a pointer to the first element of the array.
-\inputcodewithfilename{c}{code-examples/00_c/}{03_arrays.c}
+\inputcodewithfilename{c}{code-examples/00_c/00_basics/}{03_arrays.c}

semester3/spca/parts/00_c/01_basics/05_strings.tex

@@ -3,4 +3,4 @@
 with length of the array $n + 1$ (where $n$ is the number of characters of the string).
 The extra element is the termination character, called the \texttt{null character}, denoted \verb|\0|.
 To determine the actual length of the string (as it may be padded), we can use \verb|strnlen(str, maxlen)| from \texttt{string.h}
-\inputcodewithfilename{c}{code-examples/00_c/}{04_strings.c}
+\inputcodewithfilename{c}{code-examples/00_c/00_basics/}{04_strings.c}

semester3/spca/parts/00_c/01_basics/06_integers.tex

@@ -0,0 +1,9 @@
+\subsubsection{Integers in C}
+As a reminder, integers are encoded as follows in big endian notation, with $x_i$ being the $i$-th bit and $w$ being the number of bits used to represent the number:
+\begin{itemize}[noitemsep]
+    \item \bi{Unsigned}: $\displaystyle \sum_{i = 0}^{w - 1} x_i \cdot 2^i$
+    \item \bi{Signed}: $\displaystyle -x_{w - 1} \cdot 2^{w - 1} + \sum_{i = 0}^{w - 1} x_i \cdot 2^i$ (two's complement notation, with $x_{w - 1}$ being the sign-bit)
+\end{itemize}
+The minimum number representable is $0$ and $-2^{w - 1}$, respectively, whereas the maximum number representable is $2^w - 1$ and $2^{w - 1} - 1$
+
+We can use the shift operators to multiply and divide by two. Shift operations are usually \textit{much} cheaper than multiplication and division.

semester3/spca/parts/00_c/02_preprocessor.tex

@@ -0,0 +1,28 @@
+\newpage
+\subsection{The C preprocessor}
+To have \texttt{gcc} stop compiliation after running through \texttt{cpp}, the \texttt{C preprocessor}, use \texttt{gcc -E <file name>}.
+
+Imports in \lC\ are handled by the preprocessor, that for each \verb|#include <file1.h>|, the preprocessor simply copies the contents of the file recursively into one file.
+
+Depending on if we use \verb|#include <file1.h>| or \verb|#include "file1.h"| the preprocessor will search for the file either in the system headers or in the project directory.
+Be wary of including files twice, as the preprocessor will recursively include all files (i.e. it will include files from the files we included)
+
+The \lC\ preprocessor gives us what are called \texttt{preprocessor macros}, which have the format \verb|#define NAME SUBSTITUTION|.
+\rmvspace
+
+\inputcodewithfilename{c}{code-examples/00_c/01_preprocessor/}{00_macros.c}
+
+To avoid issues with semicolons at the end of preprocessor macros that wrap statements that cannot end in semicolons, we can use a concept called semicolon swallowing.
+For that, we wrap the statements in a \texttt{do \dots\ while(0)} loop, which is removed by the compiler on compile, also taking with it the semicolon.
+
+There are also a number of predefined macros:
+\begin{itemize}[noitemsep]
+    \item \verb|__FILE__|: Filename of processed file
+    \item \verb|__LINE__|: Line number of this usage of macro
+    \item \verb|__DATE__|: Date of processing
+    \item \verb|__TIME__|: Time of processing
+    \item \verb|__STDC__|: Set if ANSI Standard \lC\ compiler is used
+    \item \verb|__STDC_VERSION__|: The version of Standard \lC\ being compiled
+    \item \dots many more
+\end{itemize}
+In headers, we typically use \verb|#ifndef __FILENAME_H_| followed by a \verb|#define __FILENAME_H_| or the like to check if the header was already included before

semester3/spca/parts/00_c/02_preprocessor/00_intro.tex

@@ -1 +0,0 @@
-\subsection{The C preprocessor}

semester3/spca/spca-summary.tex

@@ -66,8 +66,9 @@
 \input{parts/00_c/01_basics/03_operators.tex}
 \input{parts/00_c/01_basics/04_arrays.tex}
 \input{parts/00_c/01_basics/05_strings.tex}
-\input{parts/00_c/01_basics/06_pointers.tex}
+\input{parts/00_c/01_basics/06_integers.tex}
-\input{parts/00_c/02_preprocessor/00_intro.tex}
+\input{parts/00_c/01_basics/07_pointers.tex}
+\input{parts/00_c/02_preprocessor.tex}
 
 
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