1. We need to count how many of the given compounds contain the carboxylic acid group $(-COOH)$.

2. Check each compound:

   (A) Sulphanilic acid
   Structure: $H_2N{-}C_6H_4{-}SO_3H$
   It contains sulphonic acid group $(-SO_3H)$, not carboxylic acid $(-COOH)$.
   So, does not contain $-COOH$.

   (B) Picric acid
   Picric acid is $2,4,6$-trinitrophenol.
   It contains a phenolic $(-OH)$ group, not $(-COOH)$.
   So, does not contain $-COOH$.

   (C) Aspirin
   Aspirin is acetylsalicylic acid. Its structure contains one carboxylic acid group $(-COOH)$.
   So, contains $-COOH$.

   (D) Ascorbic acid
   Ascorbic acid (Vitamin C) is an enediol lactone. Despite the name "acid", it does not contain a carboxylic acid group $(-COOH)$.
   So, does not contain $-COOH$.

3. Total compounds containing $-COOH$:

$1$

Therefore, the required integer answer is:

$\boxed{1}$

4. Comparison with stored correct answer:
   Stored correct answer = $1$
   Derived answer = $1$
   Hence, they agree.