Add multilingual language and systems learning tracks

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

@@ -0,0 +1,15 @@
+<!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>Square brackets send a message to a receiver: <code>[plan completed]</code>. <code>@interface</code> declares methods and <code>@implementation</code> defines them. These GNUstep exercises use explicit memory management, not Apple ARC.</p><pre><code class="language-objectivec">#import &lt;Foundation/Foundation.h&gt;
+#include &lt;stdio.h&gt;
+#include &lt;assert.h&gt;
+
+int main(void) {
+    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
+    NSArray *minutes = [NSArray arrayWithObjects:
+        [NSNumber numberWithInt:1], [NSNumber numberWithInt:2], [NSNumber numberWithInt:3], nil];
+    int total = 0;
+    for (NSNumber *value in minutes) total += [value intValue];
+    printf(&quot;%d\n&quot;, total);
+    [pool drain];
+    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://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/ProgrammingWithObjectiveC/Introduction/Introduction.html">Language reference</a></p></html>