Skip to content

Commit

Permalink
Refresh HTML pages
Browse files Browse the repository at this point in the history
  • Loading branch information
Vladimir Kotal committed Feb 26, 2024
1 parent e82f869 commit 2578bea
Showing 1 changed file with 46 additions and 46 deletions.
92 changes: 46 additions & 46 deletions 02.html
View file
Original file line number Diff line number Diff line change
Expand Up @@ -819,6 +819,52 @@ <h2><a id="user-content-suffixes" class="anchor" aria-hidden="true" tabindex="-1
<div class="highlight highlight-source-c"><pre><span class="pl-en">printf</span>(<span class="pl-s">"\110\x6F\154\x61"</span>); <span class="pl-c">// Used in a string literal.</span>
<span class="pl-en">printf</span>(<span class="pl-s">"%c\n"</span>, <span class="pl-c1">'\x21'</span>); <span class="pl-c">// Used in a character constant.</span>
<span class="pl-c">// -&gt; Hola!</span></pre></div>
<h1><a id="user-content-getchar" class="anchor" aria-hidden="true" tabindex="-1" href="#getchar"><span aria-hidden="true" class="octicon octicon-link"></span></a>getchar()</h1>
<ul>
<li>
<code>getchar</code> function reads one character from the process standard input and
returns its value as an <code>int</code>.
<ul>
<li>When it reaches end of input (for example, by pressing <code>Ctrl-D</code> in the
terminal), it returns <code>EOF</code>
</li>
<li>
<code>EOF</code> is a define, usually set as <code>-1</code>. That is why <code>getchar</code> returns
an <code>int</code> instead of a <code>char</code> as it needs an extra value for <code>EOF</code>.</li>
<li>
<code>getchar</code> needs <code>#include &lt;stdio.h&gt;</code>
</li>
<li>You can verify that <code>EOF</code> is part of <code>&lt;stdio&gt;</code>, search for "getchar"
here: <a href="https://pubs.opengroup.org/onlinepubs/9699919799" rel="nofollow">https://pubs.opengroup.org/onlinepubs/9699919799</a>
</li>
</ul>
</li>
</ul>
<h3><a id="user-content-wrench-task-write-code-that-will-read-characters-from-a-terminal-and-prints-them-out" class="anchor" aria-hidden="true" tabindex="-1" href="#wrench-task-write-code-that-will-read-characters-from-a-terminal-and-prints-them-out"><span aria-hidden="true" class="octicon octicon-link"></span></a>🔧 Task: write code that will read characters from a terminal and prints them out.</h3>
<p>It should work like this:</p>
<pre><code>$ cat /etc/passwd | ./a.out &gt; passwd
$ diff passwd /etc/passwd
$ echo $?
0
</code></pre>
<ul>
<li>Remember, we said above that an assignment is just an expression, so it has a
value. So, you can do the following:</li>
</ul>
<div class="highlight highlight-source-c"><pre><span class="pl-k">if</span> ((<span class="pl-s1">c</span> <span class="pl-c1">=</span> <span class="pl-en">getchar</span>()) <span class="pl-c1">==</span> <span class="pl-c1">EOF</span>)
<span class="pl-k">return</span> (<span class="pl-c1">0</span>);</pre></div>
<p>instead of:</p>
<div class="highlight highlight-source-c"><pre><span class="pl-s1">c</span> <span class="pl-c1">=</span> <span class="pl-en">getchar</span>();
<span class="pl-k">if</span> (<span class="pl-s1">c</span> <span class="pl-c1">==</span> <span class="pl-c1">EOF</span>)
<span class="pl-k">return</span> (<span class="pl-c1">0</span>);</pre></div>
<p>However, do <strong>not</strong> abuse it as you may create a hard to read code. Note the
parentheses around the assignment. The <code>=</code> operator has a lower priority than
the <code>==</code> operator. If the parens are not used, the following would happen:</p>
<p><code>if (c = getchar() == EOF)</code> would be evaluated as:</p>
<p><code>if (c = (getchar() == EOF))</code>, meaning that <code>c</code> would be either <code>0</code> or <code>1</code> based
on whether we read a character or the terminal input is closed.</p>
<p>We will learn more about operator priority later in the semester.</p>
<p>🔑 <a href="https://github.com/devnull-cz/c-prog-lang/blob/master/src/getchar.c">getchar.c</a></p>
<h1><a id="user-content-the-sizeof-operator" class="anchor" aria-hidden="true" tabindex="-1" href="#the-sizeof-operator"><span aria-hidden="true" class="octicon octicon-link"></span></a>The <code>sizeof</code> operator</h1>
<ul>
<li>The <code>sizeof</code> operator computes the byte size of its argument which is either
Expand Down Expand Up @@ -960,52 +1006,6 @@ <h3><a id="user-content-wrench-task-print-ascii-table" class="anchor" aria-hidde
78 x 79 y 7a z 7b { 7c | 7d } 7e ~ 7f NP
</code></pre>
<p>🔑 <a href="https://github.com/devnull-cz/c-prog-lang/blob/master/src/ascii-hex.c">ascii-hex.c</a></p>
<h1><a id="user-content-getchar" class="anchor" aria-hidden="true" tabindex="-1" href="#getchar"><span aria-hidden="true" class="octicon octicon-link"></span></a>getchar()</h1>
<ul>
<li>
<code>getchar</code> function reads one character from the process standard input and
returns its value as an <code>int</code>.
<ul>
<li>When it reaches end of input (for example, by pressing <code>Ctrl-D</code> in the
terminal), it returns <code>EOF</code>
</li>
<li>
<code>EOF</code> is a define, usually set as <code>-1</code>. That is why <code>getchar</code> returns
an <code>int</code> instead of a <code>char</code> as it needs an extra value for <code>EOF</code>.</li>
<li>
<code>getchar</code> needs <code>#include &lt;stdio.h&gt;</code>
</li>
<li>You can verify that <code>EOF</code> is part of <code>&lt;stdio&gt;</code>, search for "getchar"
here: <a href="https://pubs.opengroup.org/onlinepubs/9699919799" rel="nofollow">https://pubs.opengroup.org/onlinepubs/9699919799</a>
</li>
</ul>
</li>
</ul>
<h3><a id="user-content-wrench-task-write-code-that-will-read-characters-from-a-terminal-and-prints-them-out" class="anchor" aria-hidden="true" tabindex="-1" href="#wrench-task-write-code-that-will-read-characters-from-a-terminal-and-prints-them-out"><span aria-hidden="true" class="octicon octicon-link"></span></a>🔧 Task: write code that will read characters from a terminal and prints them out.</h3>
<p>It should work like this:</p>
<pre><code>$ cat /etc/passwd | ./a.out &gt; passwd
$ diff passwd /etc/passwd
$ echo $?
0
</code></pre>
<ul>
<li>Remember, we said above that an assignment is just an expression, so it has a
value. So, you can do the following:</li>
</ul>
<div class="highlight highlight-source-c"><pre><span class="pl-k">if</span> ((<span class="pl-s1">c</span> <span class="pl-c1">=</span> <span class="pl-en">getchar</span>()) <span class="pl-c1">==</span> <span class="pl-c1">EOF</span>)
<span class="pl-k">return</span> (<span class="pl-c1">0</span>);</pre></div>
<p>instead of:</p>
<div class="highlight highlight-source-c"><pre><span class="pl-s1">c</span> <span class="pl-c1">=</span> <span class="pl-en">getchar</span>();
<span class="pl-k">if</span> (<span class="pl-s1">c</span> <span class="pl-c1">==</span> <span class="pl-c1">EOF</span>)
<span class="pl-k">return</span> (<span class="pl-c1">0</span>);</pre></div>
<p>However, do <strong>not</strong> abuse it as you may create a hard to read code. Note the
parentheses around the assignment. The <code>=</code> operator has a lower priority than
the <code>==</code> operator. If the parens are not used, the following would happen:</p>
<p><code>if (c = getchar() == EOF)</code> would be evaluated as:</p>
<p><code>if (c = (getchar() == EOF))</code>, meaning that <code>c</code> would be either <code>0</code> or <code>1</code> based
on whether we read a character or the terminal input is closed.</p>
<p>We will learn more about operator priority later in the semester.</p>
<p>🔑 <a href="https://github.com/devnull-cz/c-prog-lang/blob/master/src/getchar.c">getchar.c</a></p>
<h1><a id="user-content-wrench-home-assignment" class="anchor" aria-hidden="true" tabindex="-1" href="#wrench-home-assignment"><span aria-hidden="true" class="octicon octicon-link"></span></a>🔧 Home assignment</h1>
<p>Note that home assignments are entirely voluntary but writing code is the only
way to learn a programming language.</p>
Expand Down

0 comments on commit 2578bea

Please sign in to comment.