Abstract
The book Innite Matrices and Sequence Spaces of Cooke is fundamental for referring to the theory of infinite matrices. So, we introduce the necessary definitions and topics related to infinite matrices in the present chapter.
Keywords: Infinite matrix, addition, product and scalar multiplication of infinite matrices, unit matrix, left and right inverse of a matrix, transpose of a matrix, lower and upper semi-matrix, orthogonal and unitary matrices, semi-continuous and continuous matrices, left and right zero-divisors of a matrix.