Add multilingual language and systems learning tracks

en/c-practice-20261101/README.md

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+# C — build and test
+
+[Agila University track](https://edu.agilaos.com/track.php?track=12&lang=en)
+
+About 15 minutes per lesson. Predict, run, change, explain, then complete the check in University.
+
+- [Lesson 1: Collections and repeated work](lesson-1/lesson.html)
+- [Lesson 2: A language feature worth understanding](lesson-2/lesson.html)
+- [Lesson 3: Build, break, and test a study planner](lesson-3/lesson.html)

en/c-practice-20261101/lesson-1/lesson.html

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+<!doctype html><html lang="en"><meta charset="utf-8"><title>Collections and repeated work</title><h1>Collections and repeated work</h1><p>15-minute session: read for 3 minutes, trace for 3, experiment for 7, and complete the check for 2. Spend longer whenever you need.</p><p>A collection stores related values. The loop visits 1, 2, and 3, updating the total from 0 to 1, then 3, then 6. Record this trace rather than guessing. Identify the first and last valid positions in this language: Pascal can declare a 1-based array, while many other examples use zero-based containers. Add another value and update the bounds correctly. Explain what an empty collection should produce.</p><p>C begins at <code>main</code>. <code>stdio.h</code> declares output functions; <code>puts</code> adds a newline. Semicolons terminate statements. An integer and a pointer are different kinds of value.</p><pre><code class="language-c">#include &lt;stdio.h&gt;
+#include &lt;assert.h&gt;
+
+int main(void) {
+    int minutes[] = {1, 2, 3};
+    int total = 0;
+    for (size_t i = 0; i &lt; sizeof minutes / sizeof minutes[0]; ++i) total += minutes[i];
+    printf(&quot;%d\n&quot;, total);
+    return 0;
+}
+</code></pre><p><strong>Expected result:</strong> <code>6</code></p><h3>Practice and evidence</h3><p>Keep three notes: your prediction, the actual result, and why they match or differ. The completion check grades understanding; the practice task builds skill.</p><p><a href="https://gcc.gnu.org/onlinedocs/gcc/Standards.html">Language reference</a></p></html>

en/c-practice-20261101/lesson-1/main.c

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+#include <stdio.h>
+#include <assert.h>
+
+int main(void) {
+    int minutes[] = {1, 2, 3};
+    int total = 0;
+    for (size_t i = 0; i < sizeof minutes / sizeof minutes[0]; ++i) total += minutes[i];
+    printf("%d\n", total);
+    return 0;
+}

en/c-practice-20261101/lesson-2/lesson.html

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+<!doctype html><html lang="en"><meta charset="utf-8"><title>A language feature worth understanding</title><h1>A language feature worth understanding</h1><p>15-minute session: read for 3 minutes, trace for 3, experiment for 7, and complete the check for 2. Spend longer whenever you need.</p><p>Use the language note below to explain this example’s state changes. Identify what is copied, what is shared, what can fail, and what is released. Only some of those questions apply to this particular program: say which ones. Make one deliberate change, predict the effect, and compare it with the actual result. A familiar-looking operator in another language may obey a different rule.</p><p>C begins at <code>main</code>. <code>stdio.h</code> declares output functions; <code>puts</code> adds a newline. Semicolons terminate statements. An integer and a pointer are different kinds of value.</p><p><code>address</code> points to the live local variable <code>completed</code>; <code>*address</code> updates that variable. Never return a pointer to an expired local or use an arbitrary numeric address.</p><pre><code class="language-c">#include &lt;stdio.h&gt;
+#include &lt;assert.h&gt;
+
+int main(void) {
+    int completed = 2;
+    int *address = &amp;completed;
+    *address += 1;
+    printf(&quot;%d\n&quot;, completed);
+    return 0;
+}
+</code></pre><p><strong>Expected result:</strong> <code>3</code></p><h3>Practice and evidence</h3><p>Keep three notes: your prediction, the actual result, and why they match or differ. The completion check grades understanding; the practice task builds skill.</p><p><a href="https://gcc.gnu.org/onlinedocs/gcc/Standards.html">Language reference</a></p></html>

en/c-practice-20261101/lesson-2/main.c

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+#include <stdio.h>
+#include <assert.h>
+
+int main(void) {
+    int completed = 2;
+    int *address = &completed;
+    *address += 1;
+    printf("%d\n", completed);
+    return 0;
+}

en/c-practice-20261101/lesson-3/lesson.html

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+<!doctype html><html lang="en"><meta charset="utf-8"><title>Build, break, and test a study planner</title><h1>Build, break, and test a study planner</h1><p>15-minute session: read for 3 minutes, trace for 3, experiment for 7, and complete the check for 2. Spend longer whenever you need.</p><p>A useful test compares a result with a requirement. The planner must never report negative remaining work for its stated nonnegative input domain. Run the starter, then deliberately remove the protection for completed counts above total. At least one check should fail. Restore it. Add two named study tasks, a summary, and boundary cases. Save the source and evidence on Agila Forge. Explain every line, including anything suggested by AI.</p><p>C begins at <code>main</code>. <code>stdio.h</code> declares output functions; <code>puts</code> adds a newline. Semicolons terminate statements. An integer and a pointer are different kinds of value.</p><pre><code class="language-c">#include &lt;stdio.h&gt;
+#include &lt;assert.h&gt;
+int remaining(int total, int done) { return done &gt;= total ? 0 : total - done; }
+int main(void) {
+    assert(remaining(4,1)==3);
+    assert(remaining(4,4)==0);
+    assert(remaining(4,5)==0);
+    assert(remaining(0,0)==0);
+    puts(&quot;Passed&quot;);
+    return 0;
+}
+</code></pre><p><strong>Expected result:</strong> <code>Passed</code></p><h3>Practice and evidence</h3><p>Keep three notes: your prediction, the actual result, and why they match or differ. The completion check grades understanding; the practice task builds skill.</p><p><a href="https://gcc.gnu.org/onlinedocs/gcc/Standards.html">Language reference</a></p></html>

en/c-practice-20261101/lesson-3/main.c

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+#include <stdio.h>
+#include <assert.h>
+int remaining(int total, int done) { return done >= total ? 0 : total - done; }
+int main(void) {
+    assert(remaining(4,1)==3);
+    assert(remaining(4,4)==0);
+    assert(remaining(4,5)==0);
+    assert(remaining(0,0)==0);
+    puts("Passed");
+    return 0;
+}