PCL: add gcd and digits_sum programs (#91)

* Add `gcd.pcl` program with links to .input and .result files

* Add `digits_sum.pcl` program with .input and .result files

Author: ntua-el21661

pcl/programs/digits_sum.input

@@ -0,0 +1 @@
+2026

pcl/programs/digits_sum.pcl

@@ -0,0 +1,23 @@
+program digits_sum;
+
+var num, sum, temp : integer;
+
+begin
+    writeString("Enter a positive integer: \n");
+    num := readInteger();
+
+    sum := 0;
+    temp := num;
+
+    while temp > 0 do
+    begin
+        sum := sum + (temp mod 10);
+        temp := temp div 10
+    end;
+
+    writeString("The sum of the digits of ");
+    writeInteger(num);
+    writeString(" is ");
+    writeInteger(sum);
+    writeString("\n")
+end.

pcl/programs/digits_sum.result

@@ -0,0 +1,2 @@
+Enter a positive integer: 
+The sum of the digits of 2026 is 10

pcl/programs/gcd.input

@@ -0,0 +1 @@
+../../alan/programs/gcd.input

pcl/programs/gcd.pcl

@@ -0,0 +1,20 @@
+program gcd;
+
+var a, b : integer;
+
+function gcd (x, y : integer) : integer;
+begin
+    if y = 0 then
+        result := x
+    else
+        result := gcd(y, x mod y)
+end;
+
+begin
+    writeString("Give me two positive integers: \n");
+    a := readInteger();
+    b := readInteger();
+    writeString("\nTheir GCD is: ");
+    writeInteger(gcd(a, b));
+    writeString("\n")
+end.

pcl/programs/gcd.result

@@ -0,0 +1 @@
+../../alan/programs/gcd.result