Question

5. Write a short technical note about Tiny C compiler. 6. What is the difference between an empty string and empty ser 7. Debugger checks for errors in compilation process. True or False? Explain. (-2 for wrong answer) 8. Explain the term Regular Language. 9. Discuss the term Context-free grammar. 10. What is an Interpreter? Write hort notes about 2 of them.

Answer 1

5)

The Tiny C Compiler (a.k.a. TCC, tCc, or TinyCC) is an x86, X86-64 and ARM processor C compiler created by Fabrice Bellard. It is designed to work for slow computers with little disk space (e.g. on rescue disks). Windows operating system support was added in version 0.9.23 (17 Jun 2005). TCC is distributed under the GNU Lesser General Public License (LGPL).

TCC has a number of features that differentiate it from other current C compilers:

• Its small file size (about 100 KB for the x86 TCC executable) and memory footprint allow it to be used directly from a single 1.44 M floppy disk, such as a rescue disk.
• TCC is intended to produce native x86, x86-64 and ARM code very quickly; according to Bellard, it compiles, assembles and links about nine times faster than GCC does.^[3]
• TCC has a number of compiler-specific language features intended to improve its practicality, such as an optional memory and bound checker, for improved code stability.
• TCC allows programs to be run automatically at compile time using a command-line switch. This allows programs to be run as a shell script under Unix-like systems that support the shebanginterpreter directive syntax.

6)

The set containing one empty string has one element. The empty set has zero elements. The one with one element is "bigger" (its cardinality is larger).

Here is a program that accepts the language that contains only the empty string:

    s = get_input();

    if (s == "") then ACCEPT;

    else REJECT;

Here is a program that accepts the empty set:

    s = get_input();

    REJECT;

They are not the same program! The first one accepts the empty string; the second does not.

8)

Regular Languages : A language is regular if it can be expressed in terms of regular expression.

Closure Properties of Regular Languages
Union : If L1 and If L2 are two regular languages, their union L1 ∪ L2 will also be regular. For example, L1 = {aⁿ | n ≥ 0} and L2 = {bⁿ | n ≥ 0}
L3 = L1 ∪ L2 = {aⁿ ∪ bⁿ | n ≥ 0} is also regular.
Intersection : If L1 and If L2 are two regular languages, their intersection L1 ∩ L2 will also be regular. For example,
L1= {a^m bⁿ | n ≥ 0 and m ≥ 0} and L2= {a^m bⁿ ∪ bⁿ a^m | n ≥ 0 and m ≥ 0}
L3 = L1 ∩ L2 = {a^m bⁿ | n ≥ 0 and m ≥ 0} is also regular.
Concatenation : If L1 and If L2 are two regular languages, their concatenation L1.L2 will also be regular. For example,
L1 = {aⁿ | n ≥ 0} and L2 = {bⁿ | n ≥ 0}
L3 = L1.L2 = {a^m . bⁿ | m ≥ 0 and n ≥ 0} is also regular.

9)

A context-free grammar (CFG) consisting of a finite set of grammar rules is a quadruple (N, T, P, S) where

• N is a set of non-terminal symbols.
• T is a set of terminals where N ∩ T = NULL.
• P is a set of rules, P: N → (N ∪ T)*, i.e., the left-hand side of the production rule P does have any right context or left context.
• S is the start symbol.

Example

• The grammar ({A}, {a, b, c}, P, A), P : A → aA, A → abc.
• The grammar ({S, a, b}, {a, b}, P, S), P: S → aSa, S → bSb, S → ε
• The grammar ({S, F}, {0, 1}, P, S), P: S → 00S | 11F, F → 00F | ε