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The nearest living sibling to ALGOL 68 may be C++, making this a good comparison candidate:

C++ doesn't have:

• nested functions,
• definable operator symbols and priorities,
• garbage collection,
• use before define,
• formatted transput using complex formatting declarations,
• assignment operation symbol (to avoid confusion with equal sign),
• arrays (and slice operations on them, but in layered libraries),
• automatic UNIONs,
• CASE expressions,
• nonlocal GOTO
• intuitive declaration syntax due to its origin from C.

ALGOL 68 doesn't have:

• public/private access protection,
• overloaded procedures (in contrast to operators),
• explicit memory allocation and deallocation,
• forward declarations,
• textual preprocessing (header files),
• confusion between &- and pointer-style,
• comment lines (only bracketed comments),
• hierarchical classes.

Code Example

Mode declaration

A new mode (type) may be declared using a mode declaration:

 int max=99;
 mode newtype = struct (
     long real a, b, c, short int i, j, k, ref real r
 );

This has the similar effect as the following C++ code:

 const int max=99;
 typedef class { 
     public: double a, b, c; short i, j, k; float &r;
 } newtype;

Note that for ALGOL 68 only the newtype name appears to the left of the equality, and most notably the construction is made - and can be read - from left to right without regard to priorities.

External references

• A comparison of PASCAL and ALGOL 68 - Andrew S. Tanenbaum - June 1977.

• Programming language comparisons
• C++
• Algol programming language family