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I'm reading a book about C programming, and I'm not sure whether there is an error in the book or not. Its about arrays and has the following array example:

enter image description here Then it says:

The following statements sets all the elements in row 2 of array to zero: for( column = 0; column <= 3; column++) a[ 2 ][ column ] = 0;

The preceding for statement is equivalent to the assignment statements: a[ 2 ][ 0 ] = 0; a[ 2 ][ 1 ] = 0; a[ 2 ][ 2 ] = 0; a[ 2 ][ 3 ] = 0;

Shouldn't it say "The following statements sets all the elements in row 1 to zero"?. Because if I say a[ 3 ] I am talking about the row 2, if I say a[ 2 ] I am talking about row 1 and if I say a[ 1 ] I am talking about row 0.

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    "Shouldn't it say "The following statements sets all the elements in row 1" instead of 2" - Do you mean, "in row 3"? Nevertheless, I don't think this is a mistake. They may use zero-based counting too. Commented Jun 6, 2014 at 3:03
  • The book's text is speaking in terms of 0 indexed to match the code. Commented Jun 6, 2014 at 3:08
  • The book is consistent with how C indexes and its own figure. Commented Jun 6, 2014 at 3:23
  • "if I say a[ 1 ] I am talking about row 0." - no, a[0] talks about row 0. Just as in the diagram in your question. Commented Jun 6, 2014 at 4:39

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C uses row-major order and zero-based indexing to reference array indices. The description you've provided of what is in the book is consistent with this.

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I would assume that the book means there are actually 3 rows in the array: #0, #1, #2. They are modifying row #2 which is the third row.

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Shouldn't it say "The following statements sets all the elements in row 1 to zero".

No. It shouldn't. In C, array indexing starts from 0. In the same book at page number 196 author said that:

The first element in every array is the zeroth element. Thus, the first element of array c is referred to as c[0], ...

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The author seems to be counting from zero, just like how arrays start from index 0 instead of index 1 in c.

As one of the comments asks: Do you mean to wonder if the author should say "row 3" instead of "row 2" since the row is indexed by 2 and so is the third row in the array?

Anyways, There is not an error in the book.

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Which row is "row 2" is a matter of convention. The picture you posted establishes that convention pretty clearly and unambiguously: rows are numbered from 0. This means that a[0][i] refers to elements in row 0, while a[2][i] refers to elements in row 2. For that reason I don't see anything wrong in that quote.

Moreover, I don't see how it could possibly be "row 1" under any meaningful convention. I wouldn't be surprised to see someone call it "row 3", but not "row 1"... Why "row 1"? Your assertion "if I say a[ 3 ] I am talking about the row 2, if I say a[ 2 ] I am talking about row 1 and if I say a[ 1 ] I am talking about row 0" suffers from the same problem. I don't see any logic in it.

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